Cylindromas, characterized by its invasive growth, contain 3.7% of all adenomas of bronchial tree (160). Two of 10 cases of tumours mestastized. However, unqualified cylindromas attaching to cancers (adenoid cystic cancer) is not justified. Histological structure of cylindromas is more variable than it is described by other authors. It is proposed to differ 4 histological variants: cribrouse, trabecular, and chondroid. Histological, histochemical and electronmicroscopical analysis allowed to discover the dual character of tumour cell secretion. As to its chemical composition, the secretion of the lumen of mucous tubulae resembles the ordinary mucus, but in cribrouse nests and across trabecular periphery and solid nests it was discovered the particular (special) secretion, rich in acid mucopolysaccharides. Feyrter's observation of endocrine activity of cylindromas are not confirmed. Tissue source of cylindromas of different localizations, in particular, bronchial may be myoepithelial cells.