Microscopic changes in the lung biopsies of 16 adult patients of both sexes without clear clinical symptoms are described. According to X-ray examination data, disseminated process in the lungs was diagnosed in 4 patients, interstitial pneumonia in 4, osteoplastic pneumopathy in 3, as well as tuberculosis, bronchiolitis and a number of others. Microscopic examination showed that the patients had various forms of petrification and ossification of the lungs, diagnosed clinically and radiologically in only 3 cases. The place of petrification of the lungs in nosology is discussed, from which it follows that we are talking about a violation of calcium metabolism, i.e. about dystrophy, and not about a storage disease. Petrification of the lungs as a precursor to ossification is a complication of various diseases, but not a self-sufficient nosological form.