Over the past years, the Institute of Oral Biology, Center of Dental Medicine, Zurich, repeatedly obtained extracted third molars showing annular gray-brown discolorations of the roots and sometimes also of the crowns. In all instances, the referring dentists were unfamiliar with this clinical appearance and worried about the possible cause. Discoloration of teeth can be due to (1) structural alterations of dental hard tissues, (2) incorporation of endogenous stains, and (3) deposition of exogenous stains (Schroeder 1997). Pigmentations caused by incorporation of stains during tooth development occur from biliverdin as a result of Morbus haemolyticus neonatorum or from porphyrin associated with porphyria, a disturbance of porphyrin metabolism. Gray-brown,