A polymorphism in the promoter region of the UDP-glucuronosyltransferase 1 (UGT1A) gene is associated with Gilbert syndrome (GS), a benign form of mild unconjugated hyperbilirubinemia. We genotyped 157 individuals from Brazil, comprising 71 Caucasians, 54 African-derived subjects, and 32 Parakanã Indians. Frequencies of the alelle (TA)7 associated with GS found in this study were 0.324, 0.407, and 0.328, respectively. The genotype frequencies differed significantly between Caucasians and African-derived individuals. The high frequencies of (TA)7 polymorphism among the three groups confirm previous data that this polymorphism is very ancient and appears to be distributed throughout the world. © 2002 Wiley-Liss, Inc.