Five different kinds of canned fish were tested on petri plates with two specially constructed mutants of Salmonella typhimurium——TA98 and TA100(Ames Test).Mutagenic activity was detected in the smoked fish of the five samples. It showed that this processed fish contained base-pair substitution mutagens which required metabolic activation.The smoked fish which was clearly positive in the test should be considered as potential human health hazards, and should be thoroughly tested in animal systems. These studies have shown that the smoked fish might possibly present traces of polycyclic aromatic hydrocarbons.