Interactive measurements of 22 quantitative parameters concerning the status and inflammation of the mucosa were taken in the rectal biopsies of patients suffering from Rheumatoid Arthritis, or with mild nonspecific morphological abnormalities (M.N.M.A.) and inflammation of the lamina propria or with Infective Colitis. The results showed that mean and standard deviation values of the rheumatoid patients are generally intermediate between those of control cases and those of M.N.M.A. and Infective Colitis. The variance analysis revealed that significant differences in some of the features exist between the four groups. Stepwise discriminant analysis helped in identifying three parameters that contributed significantly to discriminating 96.30% of the cases: Mucin area/Mucosal area; Number of inflammatory cells in the lower half/Number of inflammatory cells in the upper half of the mucosal thickness; Number of Granulocytes/mm2 of the lamina propria. Of the 27 cases included in the study, only one belonging to the control group was allocated incorrectly by the computer to the Rheumatoid Arthritis category. High correlation coefficients were observed between some of the morphometric, serological and clinical data in the rheumatoid patients. The highest values were between Number of Mononuclear cells/mm2 of lamina propria and C-Reactive Protein (+0.920) as well as between Mucin area/Mucosal area and serum IgM level (-0.950).