Pellagra due to malnutrition occurred in an Ottawa women in 1973. She was given a normal diet with supplements of riboflavin, thiamine, niacin and ascorbic acid. The clinical response was striking. Although pellagra is still common in some parts of the world, it is now rare in North America. The disease may occur secondary to malnutrition or malabsorption; inborn errors of metabolism or transport, as in Hartnup disease; deviation of precursors of niacin, as in carcinoid syndrome; or competitive inhibition of niacin incorporation into nicotinamide-adenine dinucleotide, as with administration of isoniazid.