The findings on roentgenographic and tomographic examination of the chest were compared in 63 instances of suspected pulmonary metastases. These were further compared with the findings at thoracotomy in 41 instances. Of the 60 patients, 30 had soft tissue or bone sarcomas and 30 had carcinomas arising from the colon, ovary or breast, and it also included 5 with malignant melanoma. Three patients with sarcomas had more than 1 thoracotomy. The diagnosis of pulmonary metastases by roentgenography of the chest was correct in 60 of 63 instances. Tomograms showed more lesions in 14 of 33 instances of sarcomas and 14 of 30 instances of carcinomas. Thoractomy revealed even more lesions than were detected by tomography in 21 of 26 instances with sarcomas and 8 of 15 instances of carcinomas. Of the 37 patients with a solitary metastasis detected on roentgenograms of the chest, 22 had additional lesions on the tomograms, 11 of 16 sarcomas and 11 of 21 carcinomas. At thoractomy, 9 of 10 patients with a single metastasis from sarcoma had even more lesions, while, in patients with carcinomas, tomograms were accurate. Prior to major ablative operations for sarcomas and before excision of pulmonary metastases, tomography should be done.