Hudbay Minerals (HBM) had the highest return between 2000 and 2005 by a mid-cap US stock, returning 25,012%.

ASSET	YEARS	% RETURN
Hudbay Minerals (HBM)	2000-2005	25,011.96%
Frontline (FRO)	2000-2005	9,679.96%
Companhia Energetica de Minas Gerais CEMIG Pref ADR (CIG)	2000-2005	4,575%
Amedisys (AMED)	2000-2005	2,972.15%
BRF SA ADR (BRFS)	2000-2005	2,338.81%
Meritage (MTH)	2000-2005	2,241.28%
HF Sinclair (DINO)	2000-2005	1,908.01%
Middleby (MIDD)	2000-2005	1,504.53%
Penn National Gaming (PENN)	2000-2005	1,369.44%
Sterling Construction (STRL)	2000-2005	1,246.4%
FTI Consulting (FCN)	2000-2005	1,134.81%
Range Resources (RRC)	2000-2005	1,100.48%
Comstock Resources (CRK)	2000-2005	938.64%
Royal Gold (RGLD)	2000-2005	917.56%
Gildan Activewear (GIL)	2000-2005	852.17%
Alliance Resource Partners (ARLP)	2000-2005	851.96%
Bank Ozk (OZK)	2000-2005	796.73%
St Joe (JOE)	2000-2005	783.8%
Boyd Gaming (BYD)	2000-2005	764.85%
Bancolombia SA ADR (CIB)	2000-2005	712.62%
Light & Wonder (LNW)	2000-2005	708.3%
CNX Resources (CNX)	2000-2005	696.94%
Methanex (MEOH)	2000-2005	693.09%
Seaboard (SEB)	2000-2005	687.83%
Landstar System (LSTR)	2000-2005	657.78%

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