Saw palmetto (Serenoa repens L.) is an herbal drug used to treat symptoms of benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS). There has been a report that a preparation containing this herb has caused cholestatic hepatitis in one person and some indications exist that it may have the potential to produce liver toxicity. The purpose of this study was to evaluate the effect of saw palmetto on rat liver function by measuring its effects on several enzymes and formation of malondialdehyde (MDA), a byproduct of lipid peroxidation. A significant increase in these parameters is considered an indication of liver toxicity. Thirty-six rats were divided into 6 groups of 6 animals each. They were treated for 2 or 4 weeks with a placebo or saw palmetto at doses of 9.14 or 22.86 mg/kg/body wt./day; that is, 2 x and 5 x the maximum recommended daily human dosages. After 2 or 4 weeks, the animals were sacrificed and blood was collected to prepare serum for enzyme assays, which were performed using commercially available kits. A portion of the liver was removed, and a homogenate prepared for the lipid peroxidation assay. Results showed no significant difference in animal body weight, enzyme activity, or MDA formation at either time or dosage level, as compared to controls. The data indicate that at the doses and time periods tested, saw palmetto did not produce any significant effect on the normal biological markers of liver toxicity.