Catalyst Pharmaceuticals (CPRX) had the best month in June 2011 by a mid-cap US stock in June 2011, returning 59.3%.

ASSET	MONTH	% RETURN
Catalyst Pharmaceuticals (CPRX)	June 2011	59.32%
Agilysys (AGYS)	June 2011	23.37%
Onto Innovation (ONTO)	June 2011	20.65%
Nexstar Broadcasting (NXST)	June 2011	19.68%
Grupo Financiero Galicia SA ADR (GGAL)	June 2011	18.88%
Under Armour Inc A (UAA)	June 2011	18.87%
Sandstorm Gold Ltd N (SAND)	June 2011	18.69%
Banco Macro SA B ADR (BMA)	June 2011	17.42%
Jazz Pharmaceuticals (JAZZ)	June 2011	14.68%
Melco Resorts & Entertainment (MLCO)	June 2011	14.02%
Crocs (CROX)	June 2011	13.54%
ATS (ATS)	June 2011	12.78%
Ligand Pharmaceuticals (LGND)	June 2011	12.74%
CVR Energy (CVI)	June 2011	12.73%
Sonic Automotive (SAH)	June 2011	12.58%
CarMax (KMX)	June 2011	12.18%
HF Sinclair (DINO)	June 2011	12.13%
Visteon (VC)	June 2011	12%
BorgWarner (BWA)	June 2011	11.6%
Chart Industries (GTLS)	June 2011	10.93%
Harley-Davidson (HOG)	June 2011	10.7%
Adtalem Global Education (ATGE)	June 2011	10.57%
Mesoblast (MESO)	June 2011	10.49%
Asbury Automotive (ABG)	June 2011	10.43%
Camtek (CAMT)	June 2011	10.37%

Mid-cap stocks are treated as having a market cap between $2B and $10B.