Channel catfish (Ictalurus punctatus) were immunized with bovine serum albumin (BSA) or vesicular stomatitis virus (VSV). Groups of catfish, housed in cages in a pond, were immunized by intramuscular (IM) injection of single doses of BSA or VSV or 2 doses of BSA or VSV given 1 week apart. Other groups of catfish were immunized with 1 IM injection of BSA or VSV incorporated in Freund's complete adjuvant (FCA). The antibody responses were measured at weekly intervals. Passive hemagglutination was used for detection of anti-BSA antibodies, and serumneutralization was used for detection of anti-VSV antibodies. A significant antibody response occurred in those catfish immunized with either BSA or VSV incorporated in FCA. One injection of BSA or VSV in physiologic saline induced little or no detectable antibody production. Two injections of BSA or VSV in physiologic saline induced a slight transcient antibody response between the third and fourth week post-injection.