Potential chemopreventive action of de-escalated doses of pravastatin (Pr), an HMG-CoA reductase inhibitor, on 1,2-dimethyihydrazine · 2HCl (DMH)-induced colon tumorigenesis was evaluated in ICR mice. Thirty mice each in 4 groups received an intraperitoneal injection of 20 mg DMH/kg body weight once weekly for 10 weeks, and were given drinking water dissolved Pr at the concentration of 10 ppm, 5 ppm, 1 ppm or 0 ppm (control) throughout the experiment. The incidence of colon tumors examined at week 35 was significantly lower in the Pr-treated groups than the control group: 20%, 21% and 23% vs. 55%. However, the tumor multiplicity/tumor-bearing animal was increased in the Pr-treated groups compared to the control group. Of all the tumors, 66 were adenocarcinomas in the distal colon and 5 were squamous cell carcinomas at the anus. The Pr treatment showed no hypocholesterolemic effect but did significant decrease of colonic mucosal cholesterol. The results seems to suggest that a small dose of Pr may reduce the incidence of colon cancers, perhaps being related, at least in part, to modulation of cholesterol synthesis in situ at the colonic mucosa.