Variation in growth and sexual maturity was examined for five stocks of pink salmon (Oncorhynchus gorbuscha) spawning at different times in British Columbia. In each stock, four males were mated with eight females in a nested breeding design, and the juveniles were reared for 500 d after fry emergence. Adults in early-spawning northern stocks were smaller than those in late-spawning southern ones, but pink salmon from northern stocks had faster growth rates than those from southern ones. The relative ranking within stocks of family weight remained constant after late winter in the year of maturity. Heritability of weight based upon sire variance components was usually greater than 0.9 after 150 d of rearing. Pink salmon from the earlier-spawning stocks were in a more advanced state of sexual maturity when the experiment was terminated than were those from later-spawning stocks, indicative of a significant genetic component in timing of sexual maturity.