Dual-beam sonar has been used since June 1987 to estimate abundance of chinook salmon Oncorhynchus tshawytscha in the Kenai River. During 1994, a split-beam system was run concurrently with the dual-beam system to compare several performance attributes and to test assumptions and design parameters of the current dual-beam system. The split-beam system provided advantages in its ability to determine the direction of travel for each target and the spatial distribution of fish in the acoustic beam. The dual- and split-beam systems detected similar numbers of targets. Split-beam data confirmed earlier studies showing that fish were strongly oriented to the bottom of the acoustic beam during both runs, although vertical distribution did vary somewhat by direction of travel, tide stage, and season. Estimated proportions of downstream targets ranged from 9.5% to 15.7% for different data sets, substantially higher than the 3% to 5% estimated in previous studies. Contrary to previous studies, mean target strength appeared to provide little discriminatory power for separating Kenai River chinook from sockeye salmon due to high within- and between-fish variability.