Multiple intestinal neoplasia (Min) mice are a good model for the investigation of the effects of dietary alterations in a genetic model for intestinal cancer. Previous studies have shown that selenium-enriched broccoli is protective against chemically induced colon cancer susceptibility. This study investigated whether selenium-enriched broccoli would be protective against intestinal cancer susceptibility in Min mice. Five-week-old heterozygotic male Min mice were fed an AIN-93-based diet containing either low-selenium broccoli or an equivalent amount of high-selenium broccoli for 10 wk. Mice fed the selenium-enriched broccoli had fewer (P < 0.02) small intestinal (46.4 +/- 3.7 vs. 65.6 +/- 6.1) and large intestinal (0.43 +/- 0.17 vs. 1.93 +/- 0.27) tumors than those fed an equivalent amount of unenriched broccoli. Min mice fed the selenium-enriched broccoli had small but significant (P < 0.0001) increases in plasma and liver selenium concentrations and red blood cell glutathione peroxidase activity. These results extend previous observations that selenium-enriched broccoli is protective against chemically induced mammary and colon cancer in rats.