Seventeen strains of bacteria isolated from the putrefied meats of the sei whale and mackerel were incubated in the media containing balenine, and it was found that they are able to hydrolyze balenine in a greater or lesser degree. Among 68 strains of histamine-forming bacteria isolated from the sardine and mackerel, on the other hand, only 2 strains showed the hydrolyzing activities on carnosine or anserine when incubated in media having these imidazole dipeptides. β-Alanyl-histamine and its methyl derivatives which correspond to the decarboxylation products of carnosine and its methyl derivatives were not detected throughout the experiments.