A chemical method for determining the amount of niacinamide in multicomponent preparations was developed. Neither niacin resulting from the degradation of niacinamide nor vitamin A, thiamine hydrochloride, riboflavin, ascorbic acid, ergocalciferol, or calcium pantothenate interferes. The method is based on the reaction of niacinamide with 1-chloro-2,4-dinitrobenzene, followed by the spectrophotometric measurement of the colored solution obtained after treatment with sodium hydroxide. The proposed method is at least as accurate as the methods currently in use. A structure is proposed for the colored product, and its route of formation is outlined.