In 50 patients aged 60 +/- 4 operated for colorectal carcinoma simultaneous combined radionuclide phlebography (RNP) and pulmonary perfusion scintigraphy (PPS) using 99Tcm labeled macroaggregates of the human serum albumin (MAHSA) were performed within 20 postoperative days aiming to detect deep vein thrombosis (DVT) and pulmonary thromboembolism (PTE). The aim of the study was to determine the incidence and segmental DVT localization as well as incidence, localization and clinical characteristics of developed pulmonary perfusion disorders. Deep vein thrombosis was detected in 33 (66%) patients with rather uniform distribution in vein segments. According to their scintigraphic characteristics the findings suggested recent thrombosis in almost all cases (only two of them had signs of chronic thrombosis). Of patients with detected DVT 17 (52%) had pulmonary perfusion disorders of which 10 (59%) were unilateral (7 right and 3 left) and 7 (42%) bilateral. Characteristics and extent of perfusion defects suggested very probable PTE in 11 (65%) patients and less probable in 6 (35%). It has been concluded that patients operated for colorectal carcinoma were highly exposed to DVT and PTE development which necessitates all measures contributing to their prevention.