The aim of the study was to look for unfavourable prognostic features in colorectal cancer patients after their surgical treatment as well as to evaluate the prognostic value of cellular ploidy and proliferative activity.Material and methods. A group of 71 colorectal cancer patients discharged from the hospital after surgical treatment in the years 1995-2000 was studied. The examined material was acquired from paraffin blocks of tumour segments. After histopathological verification, the tumour segments recovered from paraffin blocks were used for cytofluorometric analysis of cellular ploidy according to the Hedley method.Results. Diploid tumours were found in 45 of 71 (63.4%) colorectal cancer patients. No significant relationship between DNA ploidy and sex, age, complications, inherited susceptibility to a disease, tumour magnitude, grade of histological malignancy, or grade of clinical progression was observed. After colorectal cancer surgery, the probability of five- and ten-year survival was 44.4% and 37.1%, respectively, for the patients with diploid tumours (DI=1.0), and 38.5% and 9%, respectively, for the patients with aneuploid tumours (DI≠1.0). These differences were not statistically significant (p=0.120).Conclusions. 1. Classical clinicopathologic factors are still the best prognostic criteria for the evaluation of the future results of colorectal cancer patients' surgical treatment. 2. Determination of cellular ploidy and proliferative activity of colonic adenocarcinoma cannot increase the ability to predict prognosis based on surgical treatment.