RED URINE, erythrodontia, hydroa aestivale and hirsutism constitute a rare group of symptoms which describe the most striking of the clinical manifestations of congenital porphyria. More important than the consideration of mere rarity, however, is the fundamental significance of this constitutional anomaly as related to a more complete understanding of the normal and pathologic physiology of pigment metabolism. Indeed, the mode and site of the production and degradation of hemoglobin are still obscure, and the story of pigment metabolism, in general, is yet incomplete. Clinical material for the study of respiratory pigments is available so infrequently that each new instance of congenital porphyria, occurring as an inborn error of hemoglobin synthesis, becomes a matter of considerable interest. A typical case of congenital porphyria is, accordingly, reported, with a review of the literature on porphyria and porphyrinuria. The results of the study of this case of congenital porphyria, including isolation of