Results of transbronchial pulmonary biopsy studies of patients of different sex and age suffering from interstitial pulmonary lesion are presented. Different diagnostic value of transbronchial pulmonary biopsy (TBBP) is shown in relation to different lesions. In case of sarcoidosis its informative value, for example, is high, while in the diffuse processes such as cryptogenic fibrosing alveolitis, the data allow only suggestive diagnosis and recommendation of an open lung biopsy. In chronic nonspecific pulmonary diseases TBBP helps to clarify the character and the activity of the process involved. In some cases it is possible to reveal a latent cancer. It is suggested to use the term "allergic alveolitis" (indicating the mechanism of development of changes mentioned) when such changes as alveolitis, small granulemas and intraalveolar outgrowths are found in the biopsy specimens.