To identify quantitative trait loci (QTL) influencing early maturation (EM), body weight (BW) and condition factor (K) in rainbow trout (' Oncorhynchus mykiss'), a genome scan approach with 96 microsatellite loci across 29 linkage groups was utilized. The six inter-strain paternal half sib families used were derived from two strains that differ in the propensity for EM. Several significant QTL for EM localized to different regions in males and females, suggesting some sex-specific control. Some QTL for BW and K localized to regions identified in previous studies, as well as where candidate genes for these traits have been identified. QTL for multiple traits often co-localized, suggesting a level of genetic correlation. The highest prevalence of co-localization occurred between EM and BW. Linkage group RT-8, which has strong connections with developmental and early life history traits, had detected effects for all traits studied.