Sarepta Therapeutics (SRPT) had the highest return in July 2012 by a mid-cap US stock, returning 146%.

ASSET	MONTH	% RETURN
Sarepta Therapeutics (SRPT)	July 2012	146%
Catalyst Pharmaceuticals (CPRX)	July 2012	145.14%
TG Therapeutics (TGTX)	July 2012	35.87%
Supernus Pharmaceuticals (SUPN)	July 2012	29.56%
Steven Madden (SHOO)	July 2012	26.94%
Energy Fuels (UUUU)	July 2012	26.91%
Cirrus Logic (CRUS)	July 2012	26.66%
Sonic Automotive (SAH)	July 2012	24.87%
Kulicke and Soffa Industries (KLIC)	July 2012	24.1%
Generac (GNRC)	July 2012	23.35%
Aris Mining (ARMN)	July 2012	20.86%
Lithia Motors (LAD)	July 2012	20.19%
IPG Photonics (IPGP)	July 2012	18.88%
Group 1 Automotive (GPI)	July 2012	17.67%
Sirius XM (SIRI)	July 2012	17.39%
Galapagos NV ADR (GLPG)	July 2012	16.65%
Under Armour Inc A (UAA)	July 2012	16.6%
Grifols SA ADR (GRFS)	July 2012	16.49%
TTM Technologies (TTMI)	July 2012	16.01%
Archrock (AROC)	July 2012	15.84%
First Merchants (FRME)	July 2012	15.79%
SK Telecom Co Ltd ADR (SKM)	July 2012	15.29%
Dorman Products (DORM)	July 2012	14.88%
IAC (IAC)	July 2012	14.67%
Match (MTCH)	July 2012	14.67%

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