In the hyperlipidemia induced by fructose in rats, 5-tridecylpyrazole-3-carboxylic acid (TDPC) reduced serum triglyceride (TG) and cholesterol (CH) levels dose-dependently. The hypolipidemic profile of this compound was quite similar to that of clofibrate. In a time-course experiment, TDPC lowered serum lipid levels shortly after the treatment, and the maximum effect was observed at 4-8h, which is quite similar to the action of clofibrate. However, there were some differences between TDPC and clofibrate in the effects on lipoprotein patterns ; TDPC increased the ratio of high density lipoprotein (HDL) to very low density lipoprotein+lower density lipoprotein (VLDL+LDL)-CH in a dose-dependent manner but clofibrate did not. The hypolipidemic effect of TDPC was due to a decrease in serum lower density lipoprotein rather than high density lipoprotein. In addition, TDPC remarkably increased the rate of disappearance of exogenous triglyceride. No adverse effects of TDPC were found on parameters such as relative liver weight and hepatic lipid content.