A 'sandwich' enzyme-linked immunosorbent assay was established to detect circulating antigens of Trichinella spiralis in human sera, its sensitivity and specificity was evaluated using 4 antigens (Trichinella spiralis, Trichuris trichiura, Dirofilaria immitis and Ascaris suum), and it was found to be sensitive and specific for T. spiralis antigen. Samples of 347 individuals with suspected trichinellosis, who had eaten incompletely cooked bear meat containing larvae of T. spiralis, were examined. Among individuals showing clinical symptoms, circulating antigens were detected in 29.9%, and the prevalence of antibodies was 18.9%. Among individuals lacking clinical symptoms, antigens were detected in 21.4% and antibodies in 5.0%. It was concluded that detection of circulating antigens was more useful for making diagnoses than measurement of specific antibodies.