This study concerns the modifying effect of carbon tetra-chloride (CCl₄) on methylazoxymethanol acetate (MAM)-induced intestinal carcinogenesis in ACI rats of both sexes. Forty five animals were given CCl₄ (0.5 ml/kg body weight) through a stomach tube, followed by an i. p. injection with MAM (25 mg/kg body weight) 24 hours after CCl₄ treatment. The paired administrations were done once a week for 4 weeks and animals were observed until sacrifice 30 weeks later. Pretreatment with CCl₄ caused not only early death from chemical toxicity of MAM but also an increase in small-bowel tumors.