Although we rarely encounter pellagra in current pediatric practice in this country, it was a serious scourge during the first third of this century. The unraveling of the etiology of pellagra is as fascinating as any mystery story. Looking back on the intriguing process that led to the understanding of the cause and prevention of this disease, one can only wonder why American epidemiologists revere Snow on Cholera as the classic demontration of epidemiologic method and neglect our own masterpiece, the work of Joseph Goldberger on pellagra.