Male rats were administered diets containing the plasticizers di-(2-ethylhexyl) adipate and di-(ethyl)phthalate,, 2-ethylhexanol, hexanol, 2-ethylhexanoic acid, hexanoic acid, 2-ethylhexyl aldehyde, and hexyl aldehyde for 3 weeks, and serum triglyceride and cholesterol values were determined. Only those compounds which had been found to produce a proliferation of hepatic peroxisomes produced a decrease in both serum lipids.