For the understanding of the changing patterns of clinical features, therapies and prognosis of pyogenic liver abscesses, 178 cases admitted to the Yonsei University Medical College Hospital over the past 20 years (1971-1990) were reviewed. Additionally, these cases were divided into 68 cases of the 1970s and 110 cases of the 1980s and which were reviewed comparatively. Most liver abscesses (87%) were located in the right lobe and 36% of abscesses were multiple. The size of abscess decreased (p<0.05) and the number of abscess tended to increase (p<0.1) in the 1980s compared with that of 1970s. The pus culture was positive in 82% with a prevalence of gram (-) bacilli. Of these cultures, E. coli was the most frequently found organism (30%) and anaerobes were cultured in 12%. The common associated diseases were diatetes mellitus (14%), malignancy (17%) and pyelonephritis (5%). Diabetes mellitus was more prevalent in the 1980s (22%) than in the 1970s (1%) (p<0.05), The most common origin of abscess in decreasing order of frequency was transbiliary infection (43%), hematogenous, trauma associated portal origin. The ascending infection through the biliary tract as the origin of liver abscess have increased significantly from 31% in the 1970s to 51% in the 1980's (p<0.05). The treatment of pyogenic liver abscesses were open drainage in 63 cases (35%) and aspiration drainage in 116 cases (65%). The incidence of complications was 69% and the frequent complications were pulmonary (56%), acute renal failure (10%), peritonitie (8%), subphrenic or subhepatic abscess (8%). Overall mortality rate was 17% and the important factors associated with significant increase in mortality rate were sepsis, acute renel failure and combined malignancies. In conclusion, there was no difference in the clinical features and prognosis of pyogenic liver abscesses between the 1970's and the 1980s. However, ascending infections through the biliary tract as the etiology of liver abscesses were more common in the 1980s and the incidence of liver abscesses in critically ill patients with mslignancy or diabetes mellitus were increased in the 1980s. Sensitive antibiotics administration and proper drainage are the cornerstones of effective therapy.