High temperature- and pressure-treated garlic (HTPG) has been shown to have enhanced antioxidative activityand polyphenol contents. Previously, we reported that HTPG inhibited 1,2-dimethylhydrazine-induced mucindepleted foci (premalignant lesions) and O6-methylguanine DNA adduct formation in the rat colorectum. In thepresent study, we investigated the modifying effects of HTPG on N-ethyl-N’-nitro-N-nitrosoguanidine (ENNG)-induced pyloric stomach and small intestinal carcinogenesis in mice. Male C57BL/6 mice were given ENNG(100 mg/l) in drinking water for the first 4 weeks, then a basal diet or diet containing 2% or 5% HTPG for 30weeks. The incidence and multiplicity of pyloric stomach and small intestinal (duodenal and jejunal) tumors inthe 2% HTPG group (but not in the 5% HTPG group) were significantly lower than those in the control group.Cell proliferation of normal-appearing duodenal mucosa was assessed by MIB-5 immunohistochemistry andshown to be significantly lower with 2% HTPG (but again not 5% HTPG) than in controls. These results indicate that HTPG, at 2% in the diet, inhibited ENNG-induced pyloric stomach and small intestinal (especiallyduodenal) tumorigenesis in mice, associated with suppression of cell proliferation.