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 (DI¹1.0). 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 . Key words: large bowel adenocarcinoma, DNA ploidy, proliferative activity of large bowel adenocarcinoma Surgical treatment, with possible adjuvant therapy depending on the progression of disease, gives large bowel cancer patients the greatest possibility for recovery (1). However, as the evaluation of clinicopathologic criteria is often subjective and limited, data on prognosis are not objective, and if surgical treatment of large bowel cancer patients is unsuccessful, it is necessary to search for other unknown factors to identify the patients with a risk of a recurrence.The purpose of this study is the following: -to look for unfavourable prognostic features in large bowel cancer patients after their surgical treatment, -to evaluate the prognostic value of cellular ploidy and proliferative activity of large bowel adenocarcinoma.