Comparisons of survival, growth and sexual maturation of mixed-sex diploid and triploid brook trout (Salvelinus fontinalis) were performed during a 2-year growth trial. Survival was similar between ploidy groups, except for significantly lowers survival of triploids during the 24-hour period immediately after heat-shock treatment of the eggs, and in one instance of a dramatic temperature increase and dissolved oxygen decrease, which occurred during rearing at 7 months of age. No differences in morphometric traits or characteristics associated with sexual maturation were observed between triploid and diploid males. However, at maturation, triploid females were significantly different from diploid females in dressed weight (mean �SE) (289.9 � 11.1 vs. 222.1 � 13.5); Clark coefficient (1.92 vs.1.01); gonad weight (0.15 � 0.01 vs. 43.25 � 6.17); gonado-somatic index (0.01 % vs. 18.6%); specific growth rate (1.52 � 0.21% vs. 1.16 � 0.11%). The commercial relevance and ecological advantage for use of triploid brook trout are discussed.