The main objective of this study was to assess the histological changes of colon ephitelium in Cebus apella induced by 1,2-dimethylhydrazine (DMH) administration. Twelve monkeys, males, (aged x: 30 months) with an average body weight of 2,800 g were utilized. The DMH was injected subcutaneously at 25 mg/kg and continued once a week for 16 weeks. The body weight was assessed once a week during the first 4 months and every 30 days until the end of the experience. Histological changes of intestinal ephitelium and mucins were assessed at the end of the experience in specimens sectioned at 5 microns, stained with Haematoxylin and Eosin, PAS and Alcian blue pH 2.5. The histological and histochemical study permitted to characterize the normal morphology, as well as the mucins characteristics in the three regions: caecum, transverse colon and distal colon. The histological changes in the DMH treated animals were hyperplasia, dysplasia and mucins decreasing. The hyperplastic changes were localizated in glandular crypts, and in the epithelio located over the lymphoid nodules. The dysplastic crypts were observed in the transverse colon and in the last portion of distal colon. These lesions were located in the upper portion as well as the bottom of the mucosa. A decrease of neutral and acids mucopolysaccharides were observed in the crypts. The results of this study suggest that the DMH induced hyperplastic changes in the crypts and in the epithelium located over the lymphoid nodules and dysplastic focus, as well as a decrease of neutral and acids mucopolysaccharides.