This European Standard specifies a method for the determination of the mass fraction of niacin in foodstuffs by high performance liquid chromatography (HPLC) by three different ways of hydrolysis, acid hydrolysis (A), enzymatic hydrolysis (B) or acid/alkaline hydrolysis (C). The method has been validated in interlaboratory tests on fortified and non-fortified samples such as breakfast cereal powder, chocolate cereals, cooked ham, green peas, lyophilized green peas with ham, lyophilized soup, nutritive orange juice, milk powder and wheat flour, at levels from 0,5 mg/100 g to 24 mg/100 g. For further information on the validation data, see Annex B. A and B give similar results for niacin. In options A and B niacin is calculated as the sum of nicotinamide and nicotinic acid, and expressed as nicotinic acid [1]. Option C gives higher results than A and B for niacin with non-supplemented cereals, but similar results for other products. In option C, niacin is calculated and expressed as nicotinic acid after transformation of nicotinamide into nicotinic acid [2]. Option A is faster and cheaper than B and C. Option B is used if an exact quantification of nicotinamide and nicotinic acid is needed. This cannot be done with option A, because there is a slight transformation of nicotinamide into nicotinic acid during the acid hydrolysis. Option C quantifies total niacin. The alkaline hydrolysis is able to liberate other forms giving higher results for niacin, which in some foods such as maize and cereals are not normally biologically available, see [3], [4] and [5]. Information on a comparison between the three different ways of hydrolysis is given in Annex C.