The influence of a daily administration of lyophilized cladodes of Opuntia ficus indica (L.) Mill. (Cactaceae) on lipid metabolism was investigated in hypercholesterolemic rats. The preparation was administered either for 15 or 30 days (by gavage at a dose of 1 g/kg in aqueous vehicle in a volume of 1.5 ml/100 g b.w.). Cholesterol, HDL, LDL and triglyceride plasma levels were assayed. Statistically significant reductions in cholesterol, LDL and triglyceride plasma levels were found. The treatment was more effective after 30 days. The effects are probably due to the high fiber content of the cladodes, but other active ingredients could be operating in conjunction with this.