Abstract.-Matched numbers of Assinica and Temiscamie strains of brook trout (Salvelinus fontinalis) were stocked as fall fingerlings into two Michigan lakes. Survival, growth, movement, sex ratio, and maturity were determined for each strain to age V. Aside from a post-stocking mortality of Assinica fish, which was believed due primarily to a furunculosis infection contracted in the hatchery, there was little evidence of consistent or significant differences in the survival of either strain to age V. Long-term incremental increases in length were not significantly different among strains although Assinica tended to be significantly longer than Temiscamie at younger ages. Assinica were from 8 to 18% heavier than Temiscamie of the same length depending on the lake. There were no significant differences between the growth rates of the sexes. Sex ratios became progressively more weighted toward females each year, due to higher mortality rates for males of both strains. A majority of both strains matured at age I, and both were fully mature at age II. There was no appreciable difference among strains in vulnerability to capture by angling. Emigration rates for both strains within a lake were quite similar. Depending on the year, 40 to 90% of the populations attempted downstream movement out of the lakes during each spawning period, which could seriously deplete populations in lakes without fish barriers. Both Assinica and Temiscamie strains appear about equally suited for Michigan trout lake management.