A possible evaluation technique was devised for examing timely cholesterol synthetic activity in the rat liver. The principle of the technique is to measure the incorporation rate of 14C atoms into a few target metabolites excreted in bile with time after an intraportal injection of [1,2-14C] acetate to the conscious rats. The measuring technique, TLC-autoradioluminography (TLC-ARLG), was devised for much more accurate, quantitative, simple and quick ultramicroanalysis of radioactive metabolites than ever before. Practically, a few microliters of the bile samples were analyzed by TLC before recording of a 2-dimensional radioactive image on the TLC plate. The incorporation ratio of 14C into cholesterol to succinic acid (C/S ratio) varied such that the value found in a 24-h fasting group was less than one-tenth of that in a sufficiently fed control group. For use as an antihyperglycemic drug, the bile C/S ratio in the nicotinic-acid-dosed group was approximately one-fifth of that in the control group.