An immature female Atlantic salmonSalmo salar, caught by a commercial salmon troller off southeastern Alaska on 20 July 1990, is the first documented representative of this species in the marine waters of Alaska. Identification was based on morphology, meristic characters, and protein electrophoresis. Scale growth patterns, an eroded or clipped dorsal fin, and a high proportion of regenerated scales indicate that the fish escaped from an aquaculture pen during spring 1990. Five additional Atlantic salmon were subsequently caught by commercial fishermen in southeastern Alaska during August 1991; identification was based on morphology and color patterns, Escaped Atlantic salmon are unlikely to have a genetic impact on native Pacific salmonids, but the possibility exists that they will disseminate nonendemic pathogens or parasites.