BACKGROUND/AIMS: Klebsiella pneumoniae (K. pneumoniae) has been emerging as the leading cause of liver abscess although the most common pathogen was Escherichia coli in the past. Our study was to clarify the significance of K. pneumoniae as a pathogen of pyogenic liver abscess. METHODS: We reviewed 157 cases of pyogenic liver abscess treated at Yeungnam University Hospital from 1996 to 2001. They were classified into two groups: K. pneumoniae group and non-K. pneumoniae group. The clinical presentations, characteristics of liver abscess, laboratory findings and the results of bacteriological studies were compared. RESULTS: The K. pneumoniae group included 60 (60.6%) cases among 99 cases with positive culture. We found higher incidence of alcoholics (45.0%) or diabetes millitus (35.0%) in K. pnemoniae group. Cryptogenic cause (61.7%) was the most frequent portal entry in K. pneumoniae liver abscess. On the other hand, in non-K. pneumoniae group, the cause of portal entry was usually the secondary (23.1%) following biliary disease (61.5%). Statistically, there was no significant difference in age, sex, symptom, characteristics of abscess, laboratory findings except total bilirubin level between the two groups. CONCLUSIONS: Liver abscess caused by K. pneumoniae has emerged as an important infectious disease with new clinical significance. When clinicians see pyogenic liver abscess in patients with alcoholics or diabetes millitus, K. pneumoniae should be considered first as a cause of liver abscess.