A statistical analysis was made on 19,140 primary malignant tumors histopathologically diagnosed at Seoul National University Hospital during 9 year period from 1978 to 1986. The study was performed to understand the recent trend of the relative frequency of the primary malignant tumors among Koreans and to compare it with the previous studies using same hospital materials, twice presented in 1968 and 1978, respectively. Sex distribution of the cases was 10,025 (52.38%) males and 9,115 (47.62%) females. Among males the frequency rank was stomach (33.88%), lung and bronchus (8.73%), leukemia (7.02%), liver (4.79%) and oral cavity (4.70%). And among females it was uterine cervix (24.48%), stomach (20.45%), thyroid (7.87%), breast (6.48%) and leukemia (4.78%). The relative frequency of malignant tumors in this study was generally similar to the previous data published in 1978 at this department, except for the fact that stomach and lung cancers were more commonly seen in both sexes during this study period than the previous periods of years.