The organophosphate metrifonate has been demonstrated to produce a hypolipidemic effect in the Syrian golden hamster as demonstrated by turbidimetric analysis of lipoprotein precipitation by heparin. A sex-related difference in sensitivity to the hypolipidemia may exist, although metrifonate appears to be an effective serum cholinesterase inhibitor in both sexes. Therefore, metrifonate may be a useful probe in the investigation of organophosphate-induced hypolipidemia.