RadNet (RDNT) had the highest return between 2000 and 2001 by a mid-cap US stock, returning 1,523.5%.

ASSET	YEARS	% RETURN
RadNet (RDNT)	2000-2001	1,523.53%
Option Care Health (OPCH)	2000-2001	630.26%
FTI Consulting (FCN)	2000-2001	556.01%
Amedisys (AMED)	2000-2001	409.12%
Caesars Entertainment (CZR)	2000-2001	401.96%
Itron (ITRI)	2000-2001	399.79%
Meritage (MTH)	2000-2001	377.2%
St Joe (JOE)	2000-2001	253.09%
Ionis Pharmaceuticals (IONS)	2000-2001	251.44%
OSI Systems (OSIS)	2000-2001	250.56%
CACI International (CACI)	2000-2001	249.08%
Neogen (NEOG)	2000-2001	244.72%
Penn National Gaming (PENN)	2000-2001	238.26%
International Game Technology (IGT)	2000-2001	235.21%
M/I Homes (MHO)	2000-2001	225.15%
Cabot (CBT)	2000-2001	212.75%
Merit Medical Systems (MMSI)	2000-2001	211.33%
HF Sinclair (DINO)	2000-2001	207.93%
Primo Brands (PRMB)	2000-2001	202.86%
ICU Medical (ICUI)	2000-2001	194.22%
ESCO Technologies (ESE)	2000-2001	193.53%
White Mountains Insurance (WTM)	2000-2001	192.95%
Encompass Health (EHC)	2000-2001	178.97%
Balchem (BCPC)	2000-2001	173.33%
Powell Industries (POWL)	2000-2001	173.02%

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