Multiple primary malignant tumors were found in 62 (10.3%) of 603 patients with oral cancer who received treatment at our department from 1976 to 1995. Among them, 47 patients were male and 15 were female. Double cancers were found in 54 patients, triple cancers were found in 4, quadruple cancer was found in 1, and multicentric oral cancers with other primary malignancies were found in 3. In 54 cases with double cancers, 22 had primary malignant tumors in an other part of the body, and the rest

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... had an oral cancer as the primary tumor. In the cases with the primary cancer in the oral cavity, the cancers appeared in the tongue in 34.4% and in the oral floor in 31.3% of the cases, and the secondary tumors developed in the digestive tract in 37.5% and in the respiratory system in 25.0% of the cases. In 30% of the double cancer cases with primary oral cancer, the secondary tumor appeared within 1 year, and 75% of them died due to the secondary cancer. At the time of initial treatment and during the course of follow-up of the primary oral cancer, examination of the upper G-I tract and the chest should be performed for the early detection of synchronous and/or subsequent tumors.