Recent immigration trends have resulted in an increased prevalence of amebic hepatic abscesses in southern states and in many northern American cities. Because amebic hepatic abscesses generally do not require drainage, differentiation from pyogenic hepatic abscesses is important. We, therefore, reviewed the records of patients admitted to the UCLA Medical Center from 1968 through 1983 to compare the clinical manifestations and to access the results of treatment of pyogenic and amebic hepatic abscesses. During this 15 year period, 82 patients (42 pyogenic and 40 amebic) with hepatic abscesses were admitted. Factors which distinguished patients with pyogenic abscesses included: age greater than 50 years; jaundice; pruritus; sepsis and shock; a palpable mass; elevated bilirubin level; elevated alkaline phosphatase level, and abnormal abdominal roentgenograms. Patients with amebic abscesses of the liver were more likely to have Mexican ancestry, recently traveled to an endemic area, abdominal pain, diarrhea, abdominal tenderness, hepatomegaly and positive amebic serology. Hepatic scans and ultrasonography were excellent methods of detecting the presence of but not the type of hepatic abscess. Over-all, the mortality was 40 per cent for patients with pyogenic abscesses whereas all 40 of the patients with an amebic abscess survived. However, operative mortality was only 4.5 per cent for the 22 patients with pyogenic abscess who were managed with systemic antibiotics and surgical drainage. We conclude that many clinical and laboratory parameters can aid in the differentiation and, as a result, management of patients with pyogenic and amebic hepatic abscesses.