A total of 483 patients with pyogenic liver abscess during the years 1986 to June 1995 were studied at Chang Gung Memorial Hospital in Kaohsiung: 343 were a single abscess and 140 were multiple abscesses. Males were predominantly affected by this disease. Abdominal pain was more frequent with the single abscess than with multiple abscesses, and jaundice was more frequent with multiple abscesses. Blood levels of alkaline phosphatase, bilirubin, and creatinine and the white blood cell count were significantly higher in patients with multiple abscesses than in those with a single abscess; and the hemoglobin level was higher with single abscesses. The single abscess was usually larger than 5 cm, and the multiple abscesses were usually smaller than 5 cm. The single abscess was always located on the right side (72%) and the multiple abscesses always on the right or both sides. Single abscesses mainly had a cryptogenic origin (58.9%) and multiple abscesses a biliary origin (45.0%). Liver aspirates revealed Klebsiella pneumoniae, Escherichia coli, Streptococcus, Bacteroides, Enterococcus, among others. K. pneumoniae was more often found in a single abscess and E. coli more often in multiple abscesses. Percutaneous catheter drainage and aspiration comprised the main treatment initially, and the failure rate with multiple abscesses was higher than that with single abscesses. Surgical intervention should be considered for multiple abscesses because of the underlying disease. The overall mortality with multiple abscesses (22.1%) was higher than that with a single abscess (12.8%). Partial hepatectomy produced a low mortality rate for both single and multiple abscesses and should be considered in the presence of severe hepatic destruction by an abscess or a stone.