The first description of multiple primary tumors of the lung was reported by Billroth in 1889. In a series of 448 thoracotomies for lung cancer in the Department of Thoracic Surgery of the Geneva Cantonal University Hospital, 11 were performed in 9 men and 2 women for double metachronous lung tumors. The tumor-free time interval between the operations ranged from 9 months to 15 years, with a mean of 61 months. The tumor was in the contralateral lung in 4 patients and in the ipsilateral one in 7 cases. Pathological examination demonstrated a different histology in 4 patients (36%). Eight of the 11 patients had resectable disease. Twenty-five percent of the patients survived without recurrence for 5 years. Four patients (36%) died within one year of diagnosis of the second tumor; three of these patients did not have a resectable second tumor. The risk of development of a second primary lung carcinoma is low, less than 1-2.1% in some series, 2.7% in our series. The survival is fairly similar to that of primary lung carcinomas in general. Surgery offers the best treatment for these tumors, which is why resection of lung carcinomas should be as limited as possible. Long-term follow-up for more than 5 years and suppression of carcinogenic factors are therefore justified.