REPORTS of relationships between the blood group alleles at the B-locus and economic traits of poultry—reviewed by Briles (1960), Gilmour (1960), Nordskog (1964), and McDermid (1964)—have aroused much interest among poultry breeders. Although most studies have involved inbred egg production strains (lines), Nordskog (1964) states that a better experimental material for study of the relationships of the B-locus with economic traits might be randombred populations. Therefore it was desirable to determine whether the relationships between economic traits and the blood group alleles at the B-locus and the superiority of the heterozygote over the homozygote, which have been reported to exist in inbred populations developed for egg production, exist in a population of non-inbred meat-type birds. The results are presented in this paper.MATERIALS AND METHODSStock. In 1954 White Plymouth Rock eggs were obtained from a commercial breeder. Since then, using a pedigree system of mating, the stock…