Mark-recapture experiments were conducted to estimate the abundance of spawning lake trout Salvelinus namaycush in Paxson Lake in the Copper River drainage, and Lake Louise and Susitna Lake in the Susitna River drainage. Total abundance of mature fish was estimated by applying the sex ratio from the harvest to the estimated number of spawning males. The experiments focused on males because females do not spawn every year. The experiment conducted at Paxson Lake in 1992 generated an estimate of abundance for 1991 of 5,828 (SE = 396) mature lake trout. Spawning lake trout were found to return to the same locations to spawn each year, therefore population size estimated from mark-recapture experiments was considered a minimum estimate. An alternate estimate was derived from the mark- unmarked ratio of lake trout sampled from the harvest. The estimate from this method for 1991 was 9,124 (SE = 1,707) mature lake trout. A significant increase in the number of mature lake trout in Paxson Lake occurred from 1990 to 1991. The potential yield, estimated from the average volume of water between 8# and 12# C, was 1.01 kg ha-1 y-1 for Paxson Lake, 0.9 kg ha-1 y-1 for Lake Louise and 0.5 kg ha-1 y-1 for Lake Susitna. In each lake with significant lake trout harvests, an estimate of sustainable yield was compared to estimated harvest. Harvests from Paxson and Summit lakes, in the upper Copper drainage, may exceed sustainable levels.