Abstract: The effects of feeding convulvulus arvensis (binweed) at 0.5 and 1g/rat were investigated. Binweed produced no clinical effects or gross lesions in rats. The plant caused decreased concentration of protein in liver homogenate and inhibited the activity of phase-1 but not phase-2 drug metabolizing enzymes. In view of binweed modulating effects on drug metabolizing enzymes, consumption of binweed by human and animal should be prohibited.