Three different "sustained-action" preparations of nicotinic acid have been compared with plain nicotinic acid in the treatment of 28 patients with hypercholesteremia. The hypocholesteremic effects were similar with the 4 preparations. The most significant difference was the greater frequency and severity of side effects during treatment with the 3 sustained-action preparations, and this precluded the majority of patients from completing a 3-month period of treatment. Gastrointestinal symptoms predominated and impairment of tests of liver function were more numerous in these 3 groups. Two patients developed jaundice while on treatment with one of the sustainedaction preparations. In most instances treatment with plain nicotinic acid has been resumed without difficulty.