The passage of chinook salmon (Oncorhynchus tshawytscha) in the Kenai River was estimated using side-looking split-beam sonar technology. Early (16 May-30 June) and late (1 July-31 July) runs of Kenai River chinook salmon have been monitored acoustically since 1987. A 200 kHz split-beam sonar system has been used since 1995 to estimate numbers of migrating adult chinook salmon returning to their natal stream. From 1987 to 1994, a 420 kHz dual-beam sonar was used to generate similar estimates. We estimated the net upstream migration of chinook salmon from 16 May through 31 July 1996 to be 70,216. This estimate is comprised of 20,461 early-run and 49,755 late-run fish.