Introduction. Venous thromboembolism and disseminated intravascular coagulation are frequent complications of malignant neoplasia. Abnormally high coagulation activity and fibrinolytic inhibition induced by surgery are suggested to be responsible for frequent occurrences of coagulative disorders. Aim. The aim of this work was to assess the influence of surgery on coagulation and fibrinolitic systems during the early postoperative period in the high risk thromboembolism population, receiving heparin prophylaxis. Materials and methods. This study was carried out in a group of 19 patients (12 males and 7 females), ages from 51 to 82 (mean 66.1), all with colorectal adenocarcinoma, who underwent scheduled elective total tumor resection. Results and Discussion. Following surgical procedures the initially elevated D-dimer plasma level increased significantly. Activated partial thromboplastin time and the prothrombin time were prolonged significantly until the end of the observation period. Substantial reduction of initially normal fibrinogen concentration was revealed 6 hours after surgery, with significant increases at the 24th hour and then after 48 hours. The platelet count decreased linearly between 6 and 48 hours. The same pattern with nadir values after 48 hours was observed for antithrombin, protein C and the plasminogen plasma levels. Conclusions. Colorectal cancer and surgery significantly activate the coagulation and fibrinolytic systems, despite prophylaxis with low molecular weight heparin. Elective cancer resection is accompanied by a process resembling consumptive coagulopathy with an impairment of standard coagulation markers as well as significant reduction in natural plasma anticoagulants. Further studies are required to determine whether substitutional administration of natural anticoagulants added to routine heparin treatment in case of prophylaxis failure should be considered.