The upriver bright strain of fall chinook salmon Oncorhynchus tshawytscha was successfully reared in net pens at three locations along the Columbia River during March, April, and May in 1985, 1986, and 1987. Juvenile fish (0.6-1.5 g) were transferred from the hatchery of origin and reared in net pens at rearing densities of 0.43-4.20 kg/m3; they were released after 4-9 weeks at an average weight of about 4.5 g. Mortality was low among fish reared in the pens, and physiological development and growth were faster than in control groups reared in the hatchery. The costs of rearing fish at most of the densities tested were lower in the net pens than in concrete hatchery raceways. Off-station rearing facilities, such as net pens, offer diversity to fishery managers for stocking juvenile salmon and may prove to be an efficient method of increasing hatchery production and the return of adults to areas adversely affected by environmental alterations.