Aerial counts of chinook salmon in tributaries of the Rakaia River, South Island, New Zealand, were made several times in each spawning season from 1973 to 1976, and compared with concurrent ground counts. Smooth curves were fitted to the aerial counts and integrated to provide indices of abundance. Numbers of salmon were estimated by dividing these indices by estimates of the mean residence time offish. For the years 1973, 1974, 1975, and 1976 the numbers of salmon estimated to be in the areas counted were 4595, 5856, 14 222, and 16 702 respectively. Trap counts on one spawning tributary (Glenariffe Stream) made up between 7.6 and 15.5% of the spawning run. Such fluctuation in the proportion of the run in any one tributary may be due to the differing susceptibility of tributaries to flooding.