The comparative analysis was performed of 29 colorectal carcinomas (CC) by the original Duke's classification and quality features of tumour (i.e. nuclear and histologic grades), on the one hand, and the number of the nucleolar organizer region (NOR) as well as the mean nucleolar organizer region area (MNORA), irregularity of the nuclear shape (based on the morphometrically determined "form factor"--FF) on the semi-thin sections, on the other hand. In the same time, the quality ultrastructural analysis of CC nuclei in different stages has been also performed. The significant correlation was found among values of MNORA, clinico-pathologic stage of the disease, histologic differentiation and nuclear grade, while a number of NOR correlated exclusively with the clinico-pathologic stage of the disease. It has been concluded that determination of the number of NOR and MNORA in the nuclei of tumour cells can be an important and objective parameter in evaluation of proliferative CC activity. Accordingly, MNORA represents a more objective and more reliable indicator of proliferative tumour activities.