The Red Lakes commercial fishery is carried on in two connected lakes with a combined area of 275,000 acres. These lakes are shallow and support a large population of walleyes (Stizostedion vitreum vitreum) which is the principal commercial species. A marking study was carried on over a 3-year period to determine whether distinct populations exist in the two lakes. Monel-metal jaw tags were placed on 9,739 walleyes taken from the spawning runs of both lakes in the springs of 1949, 1950, and 1951. A total of 1,572 tags, or 16.1 percent, was returned during the 3-year period. Of the total tag recoveries 314, or 20.6 percent, moved between the two lakes. The greatest distance covered by any fish was 60 miles in 68 days and the fastest rate of travel was 41.5 miles in 33 days. The population of the two lakes was judged to be homogeneous on the basis of fish movement, similar rates of growth of fish taken from both lakes, and similar condition factor (K). Comparison of returns of marked fish at various size intervals with numbers marked in each interval suggests that mature males are completely available to the commercial nets but that females reach a size beyond which vulnerability drops appreciably. It was further demonstrated that males were not subject to exploitation before maturity but that the majority of females was subject to 1 year of fishing prior to attainment of sexual maturity.