I investigated the genetic architecture underlying variation in embryonic developmental rate in rainbow trout ('Oncorhynchus mykiss ') and tested whether there was genetic covariation with age at maturation. Both dams and sires influence the hatching time of their progeny indicating that developmental rate is under significant genetic control. Genome scans with 127 microsatellite loci from all 29 linkage groups in two families detected four significant quantitative trait loci (QTL) for developmental rate. A QTL on linkage group RT-8 explained 23.8% of the phenotypic variation and supports results from previous studies. I found inconsistent support for the hypothesis that embryonic developmental rate is genetically coupled to age of maturation. Maturation background and the maturation schedule of sires did not have a consistent effect on progeny hatching times. However, alleles associated with faster developmental rate were found significantly more often in early maturing rather than typical/later maturing male ancestors from one family.