Twenty one surgical specimens of lung cancer were studied. Microangiography showed that the vascularization of the tumours did not depend either on the size or histology of carcinoma. Abundant vascularity of tumours was associated with the degree development of connective tissue--vascular stroma. Poor vascularity was linked with neoplastic blockade of vessels and the presence of necrosis. Besides the cancer tumour the vascular changes existed in all parts of the lung, but they were expressed most profusely in the surroundings of neoplastic infiltrate. The range of histological vascular changes was as follows: elastosis, inflammation, lumen obliteration (proliferation of intima), wall thickening (arterialization of veins), oedema, hyalinization, plasmorrhagia, fibrosis (scarring), presence of acid GAG, thrombosis. The most striking vascular changes were connected with hilar and intralobar localization of the tumour, the mildest with subpleural position. The intensity of vascular changes depended on the size of tumour and existence of necrosis. The extent of necrosis and the histological type of neoplasm exerted no essential effects in this respect. Inflammatory cell infiltration appeared abundantly in the direct vicinity of the tumour in adenocarcinoma, with hilar localization and displayed proportional dependence on the size of tumour and the extent of necrosis, but the tumours, whose diameter exceeded 6 cm, failed to have any effect on the intensity of the inflammatory cell reactions.