Among 3602 blood donors from a mixed population of Bahia, Brazil the relationship between ABO blood group gene frequencies and type of family names was studied within each racial group. There are no differences in the ABO gene frequencies between Blacks or Mulattoes with and without devotional surnames. However, White blood donors bearing devotional surnames had ABO gene frequencies significantly more negroid than Whites without devotional surnames (x2-! = 12.39; p \u3c 0.01).The authors conclude that in certain populations the family name is more informative of racial identification than the individual ABO blood group phenotype