Between 1977 and 1987, 20 patients with mesothelioma were treated at Severance Hospital. Data was gathered from medical charts at the time of hospitalization of mesothelioma patients and from a follow-up questionnaire by mail or telephone. The results acquired were as follows : 1. Among the 20 patients, 11 men and 9 women with mesothelioma were identified. The mean age at hospitalization was 47 years and 11 mesothelioma patients were known or presumed to be dead during the different observation periods. 2. Only one mesothelioma patient had a definite history of occupational asbestos exposure. 3. The sites of origin of mesothelioma were the pleura(13), peritoneum(2), pericardium(2), mediastinum (2), and pelvis(1). Common symptoms included dyspnea, chest pain, abdominal distension, etc. 4. Pathologically, mesotheliomas were divided into 14 malignant types and 6 benign types ; and histologically, 8 fibrous mesotheliomas and 3 epithelial mesotheliomas were shown. 5. There was a statistically significant difference in survival rate according to pathologic type and smoking status. In the groups with malignant mesothelioma, 50% survival time from first symptoms was 18 months and that from diagnosis was 11 months. Also, 75% survival time from diagnosis was 6 months in the smoking groups and 19 months in the non-smoking groups.