The clinical course of generalized Yersinia enterocolitica infection in 13 patients was observed. Two syndromes were apparent; seven patients had an acute septicemic picture, whereas the rest had a subacute localizing infection that usually produced hepatic or splenic abscesses. The latter form often resembled amebic hepatitis clinically, and five of the six patients died despite antibiotic treatment. The acute septicemic form of the disease resembled systemic salmonellosis, and most cases responded to therapy with the appropriate antibiotics.