Tissues of the fishes are as amenable to the techniques of modern cell culture as mammalian tissues and organs, and yet this vast resource, comprising thousands of vertebrate species, remains largely unexplored. The model systems that have been developed demonstrate the utility of fish cells as sources of special adaptations and exaggerated physiological systems. In this review, we briefly describe several of the successful models along with recent developments in fish cell culture with the hope of stimulating increased interest in the lower vertebrates as useful complements to mammalian cell culture in biomedical research. The topics covered include epithelial ion transport, endocrinological studies, the cellular stress (heat shock) response, thermotolerance, cancer biology, and environmental toxicology.