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 La Arena Gold Oxide Mine ("Oxide Mine") located in Peru.


Significant intercepts were:



Hole                                    Intercept (mts)    Gold Grade (g/t)
--------------------------------------------------------------------------
CA-R11-018                                         184                0.84
CA-R11-020                                         134                2.29
CA-R11-021                                         274                0.51
CA-R11-022                                         200                1.43
CA-R11-024                                         296                0.69
CA-R11-025                                         210                0.62



Rio Alto previously announced an 11,700m RC drilling program at the Calaorco
Pit. Based on the results obtained from the first 32 holes totaling 9,029m
management has decided to increase the program by 3,000m to 14,700m in
approximately 55 holes. Rio Alto will deliver an updated resource model for the
Calaorco Pit during Q4 2011. Management expects that this drilling program will:
result in positive changes to the resource block classification; define new
resource blocks; and identify new areas to test in order to increase resources. 


On April 26, 2011 the Company reported the results from 14 holes totaling
3,755m. This announcement reports the results of an additional 9,029m in 18
holes. All holes, except one, intercepted gold mineralization in excess of the
current mining cutoff grade within and outside of the current pit design.


The results of the most recent 18 holes within the oxide breccia sandstone are
outlined below:


Drill Results 

References to "Pit Location" in the following table refer to intercepts within
("Inside") the Calaorco Oxide Pit or drill hole intercepts that extended below
("Below") the Calaorco Oxide 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/0615rio.pdf.




Hole ID              From    To  Interval (m)  Au g/t  Ag g/t   Pit Location
----------------------------------------------------------------------------
RC15                   88   104           16     0.41    0.40   Inside
RC16                  182   200           18     0.33    0.92   Inside
RC17                    0    40           40     3.44    0.28   Inside
Including              18    34           16     6.08    0.33   Inside
RC17                  112   166           54     0.36    0.21   Inside
RC17                  236   300           64     0.38    0.33   Inside
RC18                    0   184          184     0.84    0.30   Below
Including              18    54           36     2.17    0.29   Inside
RC19                  122   150           28     0.25    0.52   Inside
RC20                    4   138          134     2.29    0.59   Inside
Including              48    60           12     6.00    0.42   Inside
Including             104   114           10     6.12    0.62   Inside
RC21                    0   274          274     0.51    0.51   Below
Including              56    70           14     2.52    0.96   Inside
RC22                    0    20           20     0.28    0.21   Inside
RC22                   88   288          200     1.43    0.26   Below
Including             132   186           54     3.55    0.32   Inside
Including             174   182            8    16.02    0.20   Inside
RC23                    4    32           28     0.56    0.21   Inside
RC23                   54    78           24     0.60    0.79   Inside
RC23                  100   162           62     0.29    0.30   Inside
RC23                  178   196           18     0.58    0.56   Inside
RC23                  218   252           34     0.28    0.42   Below
RC24                    2   298          296     0.69    0.41   Below
RC25                    0   210          210     0.62    0.26   Below
Including              80    94           14     3.05    0.26   Inside
RC25                  242   260           18     0.45    0.20   Below
RC26                   72   106           34     0.72    0.62   Inside
Including              74    76            2     8.13    2.40   Inside
RC26                  246   300           54     0.32    0.41   Inside
RC27                  214   336          122     0.37    0.37   Below
RC28                   18   264          246     0.33    0.42   Below
Including              22    26            4     1.61    1.35   Inside
Including             102   108            6     1.47    0.33   Inside
Including             220   226            6     1.06    0.67   Below
RC29                   10    28           18     0.45    0.20   Inside
RC29                  104   146           42     0.19    0.58   Inside
RC30                    0    34           34     0.11    0.20   Inside
RC30                   86   106           20     0.13    0.34   Inside
RC30                  164   178           14     0.22    0.23   Inside
RC30                  264   306           42     0.20    0.31   Below
RC31                  Below the cutoff grade                                
RC32                   32    54           22     0.22    1.18   Inside



There are two RC drill rigs working at La Arena. By the end of June, four
diamond drill rigs are scheduled to arrive on site.


Approximately 500m north of Calaorco a new exploration target, Astrid, has been
identified by surface mapping and geochemical sampling. This target has the same
geological and geochemical characteristics as Calaorco. At Astrid the Company
plans to run 20 Km of IP and Ground Magnetic lines to identify drill targets. 


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
to control 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. Ian Dreyer, B.App.Sc (AUSIMM Member), of Coffey Mining Pty Ltd, a Qualified
Person as defined by National Instrument 43-101, designed and reviewed the
Quality Control and Assurance program carried out by the Company with respect to
these drill results. Each of Mr. Garay and Mr. Dreyer has read and approved the
scientific and technical information in this news release. For additional
information regarding the Oxide Mine 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 Calaorco and the announcement of an
exploration program at the Astrid target. 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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