This study was undertaken to evaluate the role of cannibalism in determining year class strength of walleyes. From mid-July 1969 to May 1970, I monitored the abundance of young walleyes by trawling and examined stomachs of adult walleyes collected in trawls and gill nets. Number of young walleyes consumed was estimated from occurrence in adult walleye stomachs, digestion rates, and estimated number of adults. Daily consumption ranged from 0.044 young walleyes per adult in August to 0.002 during the winter. Monthly cannibalism, estimated by the multiplication of daily consumption by the number of days and the number of adult walleyes, varied from 1,053,000 young in August to 240,000 during the winter. Cannibalism declined proportionally with abundance of young walleyes. Overwinter mortality rates in 1969–1970 were highest for small young-of-the-year walleyes because adult walleyes were size-selective in preying upon young.