Immunohistochemically detected MIB1 has been determined in a series of 106 colorectal carcinomas with three different evaluation methods (semiquantitative estimation, evaluation by image analysis, and cell count). Although the semiquantitative estimation correlated significantly with results obtained by image analysis (R = 0.8), both methods were only poorly associated with MIB1 counts (R = 0.5). Additionally, all three methods revealed no statistical correlation of MIB1 with the clinical outcome of the respective patients. Our results indicate a pronounced heterogeneity of MIB1 in colorectal adenocarcinoma, thus leading, irrespectively of the evaluation method used, to non-representative results with lack of clinical relevance.