Abstracf. The effect of two different single doses of a sustained release preparation of pyridyl carbinol, Ronicol Retard" taken by mouth, was studied in eleven patients. The results were compared to previously obtained data, with identical experimental procedures, for nicotinic acid and placebo.The concentration of free nicotinic acid in plasma rose slowly after 0.45 and 1.05 g of Ronicol Retard@ to reach a maximum level after 2 to 3 h and then declined to basal levels after 6 or more h.The concentration of FFA in plasma was lowered to the same level as with nicotinic acid by both doses of Ronicol Retard@. In comparison to values obtained after placebo, 0.45 g depressed the FFA levels for 1'/* h, 1.05 g for about 3 h.When the FFA lowering effect vanished there was little rebound (overshoot) of FFA levels after Ronicol Retard@ while nicotinic acid gave rise to a pronounced overshoot.Flush, similar to that seen after nicotinic acid, occurred in all patients receiving 1.05 g of Ronicol Retard". After 0.45 g not all patients showed flush, and those who did had it to a slighter degree than after 1.05 g.Compared to nicotinic acid pyridyl carbinol did not inhibit lipolysis in adipose tissue when added in vitro unless the concentration was 100 times greater than that of nicotinic acid. Even then the inhibition was much less pronounced than with nicotinic acid. This finding together with the appearance of free nicotinic acid in plasma after Ronicol Retard@ suggests that this compound lowers plasma levels of FFA by being metabolized to nicotinic acid, which then inhibits lipolysis.The relationship of lowering of FFA, the FFA overshoot and other possible effects of nicotinic acid to the lowering of the concentration of cholesterol in plasma is briefly discussed.In 1955 Altschul and co-workers (1, 2) demonstrated that nicotinic acid in high doses lowers the concentration of cholesterol in blood plasma of animals and man. It is now evident that nicotinic 22 -692999