We examined the relationship between egg number and body size for 70 steelheadOncorhynchus mykiss(formerlySalmo gairdneri) collected during 1985–1987 from the Bois Brule River and Pikes Creek, two Wisconsin tributaries to western Lake Superior. These data were compared with limited historical data from the Bois Brule River and nearby streams along the lake's north shore in Minnesota. Within the Lake Superior basin, steelhead exhibited significant variation of fecundity among spawning runs in different rivers and among years but not between spring and fall (autumn) runs in the Bois Brule River in 1985. Steelhead that spawned in Wisconsin tributaries to Lake Superior during 1985–1987 were significantly more fecund at a given size than were steelhead collected from tributaries along the north shore in Minnesota 20–25 years ago. Steelhead from Wisconsin tributaries produced egg numbers (3,000–6,900/female) similar to numbers (1,200–6,900) produced by Pacific Ocean steelhead in the same size range. Both length and weight of steelhead were strongly correlated with egg number and egg size. Age was not a good predictor of egg number. A common slope of 2.02 adequately fit all available Lake Superior data of length-fecundity relationships. The fecundity of steelhead for Wisconsin tributaries to Lake Superior can be estimated from the average equation for recent data from the two Wisconsin streams, log10y= –1.46 + 1.851og10x(y= egg number;x= total length in millimeters).