In order to study the response of channel catfish (Ictalurus punctatus) to purified protein and virus antigens, groups of fish were injected with purified bovine serum albumin and vesicular stomatitis virus (New Jersey strain). Detection of antibodies to bovine serum was carried out by the passive hemagglutination test while antibodies to vesicular stomatitis virus were detected by plaque reduction analysis. Results regarding the marked difference in response of channel catfish to purified protein antigens compared with virus antigens are discussed.