Clinical features of the first and second primaries in patients with multiple malignancies have not been extensively studied. We compared patient and treatment characteristics of the primary malignancy in 48 consequent multiple primary cancer patients with those of the second primary in the same cohort. The second primaries comprised fewer breast cancers; 29.2% of primaries as opposed to 10.4% of second tumors were breast cancer (P = 0.049). In addition, primary tumors tended to be at a lower TNM stage than secondary tumors (P = 0.060). The median overall survival after the diagnosis of the first primary for the whole cohort was 22.3 years (95% Cl, 2.0-42-5) and the median time to presentation of the second malignancy was 38 months after the diagnosis of the first primary (range, 0 to 384). Therefore, the prognosis of cancers in the multiple malignancy group appears to be good and they appear to have an indolent clinical behavior. Thus, we recommend a long screening time for secondary tumors after a curative treatment in patients with common cancers, taking into account the different occurrence patterns of second primaries with respect to first primaries.