Insmed (INSM) had the best month in 1998 by a large-cap US stock in November 1998, returning 223.9%.

ASSET	MONTH	% RETURN
Insmed (INSM)	November 1998	223.94%
Sterling Infrastructure (STRL)	December 1998	220.72%
eBay (EBAY)	November 1998	127.47%
Amazon (AMZN)	June 1998	126.67%
eBay (EBAY)	October 1998	95.01%
Telkom Indonesia (Persero) Tbk PT ADR Rep 100 B (TLK)	October 1998	84.12%
Onto Innovation (ONTO)	September 1998	80.65%
Teradyne (TER)	October 1998	79.93%
Coeur Mining (CDE)	September 1998	77.27%
Amkor Technology (AMKR)	December 1998	76.53%
ASML Holding NV New York Registry Shares (ASML)	October 1998	74.36%
MicroStrategy (MSTR)	June 1998	73.85%
Amazon (AMZN)	December 1998	73.19%
Advanced Energy Industries (AEIS)	October 1998	69.35%
Newmont Goldcorp (NEM)	September 1998	68.69%
Arrow Electronics (ARW)	October 1998	68.6%
PTC (PTC)	October 1998	66.25%
Skyworks Solutions (SWKS)	December 1998	65.52%
Old Dominion Freight Line (ODFL)	November 1998	62.47%
Manhattan Associates (MANH)	December 1998	60.29%
Harmony Gold Mining (HMY)	April 1998	59.82%
Mitsubishi UFJ Financial Group Inc ADR (MUFG)	October 1998	59.18%
Charles Schwab (SCHW)	December 1998	59.02%
Credicorp (BAP)	November 1998	58.56%
Kinross Gold (KGC)	September 1998	58.06%

Large-cap stocks are treated as having a market cap of $10B+.