A standardized extract of the fruits of Solanum distichum has previously been shown to possess anti-hypertensive activity in rats (ED50 about 1 mg/kg). Earlier acute toxicity studies had shown that single doses up to 2g/kg orally or intraperitoneally failed to show any signs of morbidity. To study its potential long-term toxicity, rats of either sex were fed orally 1g/kg of the extract daily over a period of 4 weeks to 6 months. The extract did not affect food intake or rate of growth of the animals. Blood counts and other hematological parameters remained unaffected. Treatment for 4 weeks had no effect on plasma cholesterol or blood urea nitrogen in both sexes, but extended treatment to 6 months tended to lower both parameters. Plasma creatinine, liver enzymes and fasting blood sugar, plasma electrolytes, total protein and albumin were not altered. Gross necropsy showed a 20% increase in liver to body weight ratios after 6 months. None of the body organs tested showed any histopathological changes. Bearing in mind that the dose of the extract used in this study was several 100 times greater than its ED50, the present findings point to the wide safety margin of the extract.