OBJECTIVE To investigate the epidemiological and clinical features of multiple primary malignant neoplasms (MPMNs). METHODS One hundred and twenty-five cases of more than or equal to three primary malignant neoplasms detected in the period of 1958 to 2001 were studied retrospectively in terms of frequency, age of onset, sex ratio, tumor location and the interval between sequential tumors. RESULTS The overall incidence of MPMNs was 0.090%; for three, four and five MPMNs was 0.078%, 0.009% and 0.001%. The mean age of onset of MPMNs was 64 years. The sex ratio, of male to female, was 1.0:1.2. The mean time interval was 7.1 years, and it reduced from 5.7 to 2.4 years in a descending order of the first, second, third, forth and fifth primary tumors. Three, four and five primary malignant neoplasms were predicated respectively in the large intestine, breast, lung, esophagus, uterus, skin; the large intestine, breast, skin stomach, urinary bladder, uterus; and the large intestine, breast, skin, parotid glands. CONCLUSIONS The overall incidence of multiple primary malignant neoplasms seems to ascend. The age of onset of MPMNs tends to be increase. The incidence of in women is higher than in men. The time interval from the first to fifth primary tumor is decreasing. The susceptible organs are identical organ, bigeminal organs or organs of the same system.