The usefulness of combining aerosol induction with Saccomanno's concentration method was examined in 240 patients who were diagnosed as having lung cancer by fiberoptic bronchoscopy and /or by thoracotomy. By the combined method, satisfactory sputum was obtained from 97.1% of the patients. Sputum cytology gave a positive diagnosis in 57.5% of the patients. Positive rates were 84.8% for patients with centrally located lung cancer and 38.3% for patients with peripherally located lung cancer. With regard to histological classification, positive rates of sputum cytology were 36.9% for adenocarcinomas, 76.8% for squamous cell carcinomas and 73.3% for small cell carcinomas. This combined method resulted in a improved yield of satisfactory sputum as well as positive cytology compared with a conventional method using spontaneous sputum, which gave only 23.3% positive cytology. The combined method may be useful for the diagnosis of lung cancer in mass surveys.