Selective brushings were conducted for all the respective segmental bronchi in both lungs of 105 patients with positive or suspected positive indications of lung cancer as revealed by sputum cytology. As a result, borderline lesions, 16 cases with 18 lesions and lung cancer, 51 cases with 58 lesions, were diagnosed. The percentage of localized lesions was 47.1% for Class III cases, 82.4% for Class IV cases and 100% for Class V cases; on the whole, identification was possible in 62.9% of all the cases. Comparison of the diagnoses made before and after all the branch brushings showed that, after the brushings, the rate of localization increased from 14.7% to 47.1%, and diagnosis of borderline lesions is also possible. Regarding the results obtained at the first examination, the rate of localization increased from 64.1% to 93.9%, and in particular, an improvement from 0% to 88.9% was noted for those cases where bronchoscopic findings had not been obtained. Based on the above results, it was concluded that the application of this brushing method is of value in the following cases: diagnosis of cases otherwise difficult to diagnose, detection of borderline lesions, and diagnosis of concurrent multiple primary lung cancer. In addition, this brushing method has made possible the detection of multiple intraepithelial lesions, leading to a more precise diagnosis of cells of the respiratory system in the near future.