Phytosterols (PS) are the analogues of animal cholesterol in various plants. beta-Sitosterol is a PS used in margarines and natural remedies to lower elevated serum cholesterol levels. PS enter the ecosystem via pulp mill effluents. The study investigated the endocrine and metabolic effects of PS on the female raccoon dog (Nyctereutes procyonoides), a canid omnivore. Eight female animals were exposed perorally to 8 mg PS/kg/d for 4 wk with 8 animals in the control group. In the PS-treated females, there was a transitory decrease in the plasma estradiol concentrations with an increase in the plasma follicle-stimulating hormone levels. The plasma triiodothyronine concentrations were higher in the PS group. Serum lipid concentrations decreased in PS-treated and control animals. This probably represents a seasonal adaptation. Most of the cholesterol in raccoon dog serum was high-density lipoprotein cholesterol, unlike that in humans but similar to some other carnivores. Liver and kidney ethoxyresorufin O-deethylase activities were lower in the PS treated females. Data indicate that raccoon dogs may not be a sentinel species for PS effects.