Seeds of the weed Datura ferox are frequent contaminants of raw materials used for animal feed. These seeds produce various toxic effects and contain mainly the alkaloids scopolamine and hyoscyamine. In this 3-month toxicity study, a mixture of scopolamine and hyoscyamine (98:2) was incorporated at four total alkaloid levels (1.5, 15, 75 or 150 mg/kg feed) into a control diet fed to 100 broilers. Alkaloid feeding caused significant reductions in the body weight gain of birds, especially of those fed a dose of 150 mg alkaloid/kg feed. Growth-retarding effects, however, were transient, as no changes in body weight gain were noted after 52 days of alkaloid feeding. Alkaloid-treated broilers showed no significant differences from controls with respect to the cardiac rate and breathing frequency nor in relation to plasma aspartate aminotransferase, alanine aminotransferase and alkaline phosphatase activities. In contrast, plasma leucine aminopeptidase activity was significantly reduced after 3 months in all alkaloid-fed birds. Autopsy and histological examination of tissues by light and electron microscopy revealed no pathological changes associated with alkaloid feeding. Broilers appeared generally healthy and behaved normally throughout. These data should be considered in the formulation of new, improved regulations defining the maximum allowable alkaloid content of D. ferox seeds contaminating raw materials destined for use as broiler feed.