Genetic variation in chinook salmon (Oncorhynchus tshawytscha) from ten hatcheries along the Columbia River drainage and the Oregon coast was described from results of starch gel electrophoresis. Highly significant differences were found between spring and fall chinook in the Columbia River watershed. It was suggested that frequencies of malate dehydrogenase, tetrazolium oxidase, and phosphoglucomutase phenotypes may be influenced directly or indirectly by selective forces.