Thirty nine cases of multiple primary malignant tumors examined at the Department of Pathology, Keimyung University School of Medicine during the period from November 1974 through March 1986 were analysed clinicopathologically. The findings are as follows: 1) Thirty nine cases had synchronous lesion and six cases metachronous lesion. The second primary malignancy occurred mean 4.7 years after the first malignancy in patients with metachronous lesion. 2) The age at diagnosis of the first malignancy ranged from 26 to 76 years, the average being 51.8 years. The male-female ratio was slightly less than 1:1.2. 3) The most commonly involved site in multicentric origin was gastrointestinal tract (44.4%) with all adenocarcinoma and the second urogenital system (29.6%). In cases of different tissues or organs (11 cases), ovary was the most frequent site (5 cases), followed by cervix (4 cases). 4) Multiple primary malignant tumors of urogenital system were all eight cases and six cases among them (75%) had smoking and drinking habits. 5) The detailed informations about possible environmental, familial and host factors necessary for the investigation of multiple primary tumors were lacking in most cases. Therefore, the history taking with special attention to these factors must be carefully recorded. And also, we suggest that in the high-risk individuals, careful follow-up and thorough search for early cancer detection or prevention should be taken.