19 patients with bilateral simultaneous pulmonary metastases were operated on between 1954 and april 1976 at the Marie-Lannelongue surgical centre. Sarcomas were twice as common as carcinomas. In 10 cases the thoracotomy was only unilateral, either because thoracotomy was not attempted on the other side owing to the diffuse nature of the lesions (8 cases) or because prior chemotherapy had permitted complete reduction of the metastases on the opposite side (2 cases). This thoracotomy remained exploratory in 47 p. cent of cases, radical removal of all the tumour nodules was possible in 53 p. cent of cases (10 patients). Peripheral resections of the lesions were the rule. But in 4 cases, lobectomy was carried out on one side. 7 of the 9 bilateral operations were performed during the same stage. There were no operative deaths. The late results are encouraging considering the number of sarcomas in which the prognosis is usually poor. Bilateral lesions are thus not an absolute contra-indication, provided one remains within reasonable anatomical and functional limits, in the fields of well-conducted anti-cancer strategy.