During the past 10 years, 54 patients, all men, were found to have roentgenographically occult lung cancer. The mean age was 61 years (range 45 to 76 years). All patients had abnormal findings on sputum cytologic study (carcinoma in 41 patients and squamous cell atypia in 13). The cancer was localized by bronchoscopy in all patients (range one to five examinations, mean 1.5). Seventy-five percent of the tumors were localized within 169 days of the abnormal sputum cytologic examination. Pulmonary resection for cure was performed in all patients: lobectomy in 38, pneumonectomy in nine, and bilobectomy in seven. Operative mortality was 5.6% (three patients). Fifty-eight cancers were resected, all squamous cell carcinomas (two had a component of large cell cancer). Tumor TNM classification (AJC) was TIS N0 M0 in 19 patients, T1 N0 M0 in 25, T1 N1 M0 in five, T2 N1 M0 in four, and T3 N0 M0 in one. Overall 5 year actuarial survival rate (lung cancer deaths only) was 90%. Five-year survival rate for the 44 patients with TIS N0 M0 and T1 N0 M0 neoplasms was 91%. Currently, 21 patients have died, but only 10 of lung cancer. Subsequent additional lung cancer developed in 12 patients (22%). Eleven of these patients had a second primary squamous lung cancer, six of which again were occult. We conclude that patients with occult lung cancer have a strong likelihood of long-term survival if treated early. Close surveillance is indicated because of the high incidence of a second primary lung cancer.