Rio Alto Mining Limited ("Rio Alto" or the "Company") (TSX
VENTURE:RIO)(OTCQX:RIOAF)(BVLAC:RIO)(DBFrankfurt:MS2) is pleased to report assay
results from 18 reverse circulation ("RC") drill holes within and around the
Calaorco Pit at the Company's La Arena Gold Oxide Mine ("Oxide Mine") located in
La Libertad, northern Peru.


Significant intercepts were:



Hole            Intercept (mts)    Gold Grade (g/t)
--------------------------------------------------
CA-R11-038                 158                0.58
CA-R11-039                 200                0.46
CA-R11-047                 238                1.06
CA-R11-049                 148                0.65
CA-R11-050                 104                1.72
CA-R11-050                 158                0.51



The following results are from the last 18 RC holes drilled at Calaorco with 15
out of the 18 holes intersecting gold mineralization above the mining cutoff
grade. These drill holes were within ("Inside") and extended outside or below
("Below") the current design of the Calaorco Pit.


A total of 13,674 metres of RC drilling in 50 holes has been completed at the
Calaorco Pit and this drill program is complete for this year. The Company's
geologists are interpreting the data generated by these 50 holes to calculate an
updated resource estimate for the Calaorco Pit. Management expects that this
drilling program will result in positive changes to the resource block
classification; define new resource blocks; and given that the deposit is open
to the northwest and southeast identify new areas to test in order to increase
resources. The updated resource estimate for the Calaorco Pit is planned for
release in Q4 2011.


Drill Results

References to "Pit Location" in the following table refer to intercepts within
("Inside") the Calaorco Pit or drill hole intercepts that extended outside or
below ("Below") the Calaorco Pit. A map illustrating drill hole locations and
selected drill hole cross sections related to this press release may be accessed
by following this link: http://media3.marketwire.com/docs/FiveMapsRIO.pdf.




--------------------------------------------------------------------
                                                                 Pit
Hole ID         From      To  Interval    Au g/t    Ag g/t  Location
--------------------------------------------------------------------
RC33             240     286        46      0.28      0.42    Inside
--------------------------------------------------------------------
RC34                         Below the cut off grade                
--------------------------------------------------------------------
RC35             180     226        46      0.20      0.37    Inside
--------------------------------------------------------------------
RC36                         Below the cut off grade                
--------------------------------------------------------------------
RC37                         Below the cut off grade                
--------------------------------------------------------------------
RC38               4     162       158      0.58      0.33    Inside
--------------------------------------------------------------------
 Including        52      64        12      1.87      0.33    Inside
--------------------------------------------------------------------
 Including        92     148        56      0.76      0.49    Inside
--------------------------------------------------------------------
RC39              30     230       200      0.46      0.41    Inside
--------------------------------------------------------------------
 Including        66      84        18      2.23      0.83    Inside
--------------------------------------------------------------------
RC40             124     142        18      0.78      0.52    Inside
--------------------------------------------------------------------
RC40             278     296        18      0.59      0.32     Below
--------------------------------------------------------------------
RC41               0      22        22      0.43      0.20    Inside
--------------------------------------------------------------------
RC41             220     238        18      0.38      0.81     Below
--------------------------------------------------------------------
RC42              76     146        70      0.21      0.47    Inside
--------------------------------------------------------------------
RC42             180     218        38      0.12      0.25     Below
--------------------------------------------------------------------
RC42             246     291        45      0.32      0.47     Below
--------------------------------------------------------------------
RC43               0      30        30      0.52      0.42    Inside
--------------------------------------------------------------------
RC44              84     146        62      0.37      0.65    Inside
--------------------------------------------------------------------
RC44             244     300        56      0.22      0.35     Below
--------------------------------------------------------------------
RC45              66     134        68      0.28      0.61    Inside
--------------------------------------------------------------------
RC45             204     210         6      0.54      1.47     Below
--------------------------------------------------------------------
RC46              20      34        14      0.51      0.33    Inside
--------------------------------------------------------------------
RC47               0     238       238      1.06      0.44     Below
--------------------------------------------------------------------
 Including        18      90        72      1.36      0.59    Inside
--------------------------------------------------------------------
 Including       160     168         8      8.33      0.83    Inside
--------------------------------------------------------------------
 Including       220     238        18      1.54      0.32     Below
--------------------------------------------------------------------
RC48               0      92        92      0.97      0.26    Inside
--------------------------------------------------------------------
RC48             128     166        38      0.86      0.45    Inside
--------------------------------------------------------------------
RC49               0     148       148      0.65      0.68    Inside
--------------------------------------------------------------------
 Including        36      72        36      2.10      1.49    Inside
--------------------------------------------------------------------
RC49             186     236        50      0.13      0.29     Below
--------------------------------------------------------------------
RC49             256     274        18      0.24      0.40     Below
--------------------------------------------------------------------
RC50               0     104       104      1.72      0.38     Below
--------------------------------------------------------------------
 Including        56      98        42      2.61      0.61     Below
--------------------------------------------------------------------
RC50             142     300       158      0.51      0.60     Below
--------------------------------------------------------------------
 Including       144     180        36      1.32      0.76     Below
--------------------------------------------------------------------



Sulphide Drilling Program

The drilling program at the La Arena Copper/Gold sulphide project started this
week. The Company has three diamond core drilling rigs on site with a fourth due
in August. The current program involves drilling 55 diamond core holes for a
total of 32,330 metres. Drilling depth will vary between 400 to 750 m in order
to: upgrade the category of resource blocks from inferred to indicated; define
new resource blocks; and identify new areas to test in order to increase
resources. During the past 6 months, in preparation for the sulphide drilling
program, the Company's geological team has reinterpreted the mineral
distribution, structures, lithology and alteration of the pre-existing
geological model. This reinterpretation will be tested by the planned 55 holes.


Astrid Prospect (Oxides)

On June 15, 2011, the Company announced that the Astrid Prospect, a gold oxide
exploration target, located approximately 500 metres north of the Calaorco Pit
had been identified by surface mapping and geochemical sampling. This target has
the same geological and geochemical characteristics as Calaorco and contains
gold mineralization hosted in oxidized brecciated sandstone. The current surface
footprint of the Astrid Prospect is 500 metres by 200 metres, over which the
Company is conducting a 14 Km IP (induced polarization) and Ground Magnetic
survey. The Company plans to start a first pass RC drilling program at Astrid in
late August.


Quality Control and Assurance

Sampling of the reverse circulation drilling and sample preparation were
performed by Rio Alto personnel and were carried out under strict protocols
recommended in the NI 43-101 Technical Report dated July 31, 2010 prepared by
Coffey Mining Pty Ltd for the Company (the "Report"). Samples were taken every
2m and split in half to yield seven to ten kilogram samples. Drill sample
recovery was generally in excess of 90%. Rio Alto has a rigorous QA/QC program
over the chain-of-custody of samples and the insertion of blanks, duplicates,
and certified reference standards in each batch of samples. Samples were shipped
to CIMM-Peru in Lima where they were dried, crushed, pulverized, and assayed.
All gold assays were obtained by standard 50g fire assaying with AA finish. All
silver assays reported in the press release were obtained by Aqua-Regia
dissolution followed by ICP measurement. CIMM-Peru is an ISO 9001:2000 certified
laboratory.


Enrique Garay, M Sc. P. Geo. (AIG Member), Vice President Geology of Rio Alto is
the Qualified Person responsible for the management of the exploration program
and disclosure of the drill results as defined by National Instrument 43-101.
Mr. Garay has read and approved the scientific and technical information in this
news release. For additional information regarding the Oxide Mine and the
sulphide project please refer to the Report, a copy of which is available under
Rio Alto's SEDAR profile at www.sedar.com.


This news release contains certain forward-looking information including
statements concerning the expected timing for the arrival of drills at La Arena,
the timing of a new resource estimate for the Calaorco Pit and the timing and
scope of exploration programs at the Company's sulphide project and Astrid
prospect. All statements included herein, other than statements of historical
fact, are forward-looking information and such information involves various
risks and uncertainties. There can be no assurance that such information will
prove to be accurate, and actual results and future events could differ
materially from those anticipated in such information. A description of
assumptions used to develop such forward-looking information and a description
of risk factors that may cause actual results to differ materially from
forward-looking information can be found in Rio Alto's disclosure documents on
the SEDAR website at www.sedar.com. Rio Alto does not undertake to update any
forward-looking information except in accordance with applicable securities
laws.


To learn more about Rio Alto Mining Limited, please visit: www.rioaltomining.com
or Rio Alto's SEDAR profile at www.sedar.com.


ON BEHALF OF THE BOARD OF RIO ALTO MINING LIMITED

Alex Black, President & COO

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