The term ‘niacin’ is used as a generic description of nicotinic acid and nicotinamide with pyridine as the basic structure. Nicotinic acid and nicotinamide function mainly as precursors of the co-enzymes NAD and NADP. Thus, nicotinamide has physiologically critical roles in mitochondrial respiration and in the metabolism of carbohydrates, lipids, and amino acids. Oral administration routes of nicotinic acid and nicotinamide via feed or water for drinking were considered bioequivalent. Niacin is safe for the target animals with a margin of safety that is at least ten times the requirements and use levels. The FEEDAP Panel assumes that exposure figures for a population already include the contribution of edible tissues and products of animals fed niacin-supplemented diets. Information on niacin metabolism and the limited data available on retention in edible tissues and products indicate that supplemental levels in feeds even far higher than the requirements (1–35 mg/kg feed) are highly unlikely to lead the tolerable upper intake level being exceeded. The FEEDAP Panel considers that the use of niacin in animal nutrition is not of safety concern for consumers. Nicotinic acid and nicotinamide are not irritant to skin, but can cause irritancy to eyes and mucous membranes. They are unlikely to cause skin sensitisation. Workers might be exposed to a respirable dust when handling nicotinic acid, which should be regarded as being potentially harmful to their health. Nicotinamide is considered to be of no concern for inhalation exposure. The use of nicotinic acid and nicotinamide in animal nutrition does not pose a risk to the environment. Nicotinic acid and nicotinamide are regarded as effective sources of niacin in animal nutrition.