Homing and straying patterns of fall chinook salmon Oncorhynchus tshawytscha originating from five Columbia River hatcheries were assessed from coded-wire-tag data for the 1977, 1978, and 1979 brood years. There was considerable variation in both the tendency of different populations to stray and where they strayed. Homing ranged from 90.1% (of 372 fish) for the Lewis River to 72.5% (of 342 fish) for the Cowlitz River. Very few chinook salmon strayed into the Washougal River and Abernathy Creek, but the Lewis and Kalama rivers attracted many strays. The numerous strays from the Cowlitz River in 1980 probably were influenced by volcanic ash from Mount Saint Helens, Washington. Apart from the Cowlitz River fish, homing varied interannually from 8 to 19.3%. More older chinook salmon strayed than did the youngest age-group. The overall levels of straying were higher than have generally been reported for salmon and, if continued, could cause substantial genetic interchange among populations