Although epidemiological studies have implicated red meat as increasing colon cancer risk, animal studies have generally not been supportive of such an effect. This study examined red meat components, such as beef protein and tallow, on markers of colon cancer risk. Rats administered dimethylhydrazine were fed either casein or beef protein as the protein source and soybean oil or tallow as the fat source in a 2 × 2 factorial design for 9 wk. There were fewer preneoplastic lesions [aberrant crypt foci (ACF)] and a greater apoptotic labeling index (P < 0.05) in the distal colonic mucosa of rats fed tallow compared with soybean oil. Fecal bile acid concentrations were significantly lower in rats fed tallow compared with soybean oil. There were no significant differences in mucosal cell proliferation. No significant effects were found due to protein source or to interactions between fat and protein sources for ACF, cell proliferation labeling indexes, or bile acid concentrations. However, there was a significant protein by fat source interaction for the apoptotic labeling index. The decreased number of ACF, decreased fecal bile acid concentration, and increased mucosal apoptosis with tallow consumption are not consistent with a role for this fat in increasing risk of colon cancer.