TG Therapeutics (TGTX) had the highest return in January 2008 by a mid-cap US stock, returning 80.2%.

ASSET	MONTH	% RETURN
TG Therapeutics (TGTX)	January 2008	80.18%
DRDGOLD Limited ADR (DRD)	January 2008	61.9%
M/I Homes (MHO)	January 2008	42.93%
ArcBest (ARCB)	January 2008	41.89%
NovaGold Resources (NG)	January 2008	38.67%
WesBanco (WSBC)	January 2008	32.98%
Stewart Information Services (STC)	January 2008	31.1%
First Bancorp (FBP)	January 2008	30.14%
Buckle (BKE)	January 2008	26.9%
KB Home (KBH)	January 2008	26.73%
Popular (BPOP)	January 2008	25.53%
Pool (POOL)	January 2008	24.7%
First Merchants (FRME)	January 2008	24.37%
Ufp Industries (UFPI)	January 2008	22.92%
Seacoast Banking Corporation of Florida (SBCF)	January 2008	20.85%
United Community Banks (UCB)	January 2008	20.61%
ATS (ATS)	January 2008	20.23%
Landstar System (LSTR)	January 2008	19.15%
AZZ (AZZ)	January 2008	18.9%
Werner Enterprises (WERN)	January 2008	17.71%
Centerra Gold (CGAU)	January 2008	17.5%
Zions Bancorporation (ZION)	January 2008	17.07%
Compania de Minas Buenaventura SAA ADR (BVN)	January 2008	16.29%
Merit Medical Systems (MMSI)	January 2008	16.1%
Knight Transportation (KNX)	January 2008	15.76%

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