Fish populations were checked in three Minnesota trout streams by the electrical-shock method. Total weights of fish per acre varied from an average of 251.1 pounds in 18 streams of the Root River system to 50.3 pounds in the North Shore system. Trout (brook, brown, and rainbow) varied from 17.3 percent of the total in the former system to 72.0 percent in the latter. The structure of the trout population in the northern streams showed more or less normal size distribution but in the other systems 6- to 9-inch trout predominated almost to the exclusion of the smaller fish. It is presumed that in the latter streams most fish are derived from planted stock.