Changes in the concentration of long-chain free fatty acids were determined gas chromatographically from inside and outside muscle samples of brine- or plate-frozen Pacific halibut and chinook salmon stored for 9–81 weeks.With both species the concentration of individual free fatty acids was greater in outside muscle than in inside muscle. Few differences in concentration of free fatty acids were noted between plate- and brine-frozen samples. Numerous free fatty acids increased significantly in concentration during frozen storage. For both species the increase was most rapid during the first 26–45 weeks of storage. The detection of flavor differences was unrelated to the concentration of individual free fatty acids.