Pulmonary nodules of unknown nature may be cancerous and are best treated by early resection. During the past 20 years we have seen 65 patients in whom asymptomatic pulmonary nodules from 5 to 20 mm in diameter were discovered on routine roentgenograms between 1 and 4 years prior to their referral to surgery. These patients have not been investigated for cancer. Instead, they had been 'observed' or treated with antibiotics while their nodules increased in size. At the time of referral, 29 patients had widespread metastases, 28 had locally invasive State III lung cancer, eight had Stage I or Stage II lesions. Only 16 patients had their tumors resected. Sixteen patients (24.6%) survived 1 year or longer; six patients (9.3%) survived more than 2 years. Early resection of all undiagnosed pulmonary nodules is essential. 'Expectant' or antibiotic treatment of these lesions should be condemned. Educational programs for family physicians are urged.