In Italian patients with high hemoglobin A(2) beta-thalassemia trait, the synthesis of beta-chains of adult hemoglobin in the peripheral blood is approximately one-half that of alpha-chains. In this study the relative rates of beta- and alpha-chain synthesis were determined in 26 Negro heterozygotes and five homozygotes for beta-thalassemia in six families. The beta/alpha ratio of globin synthesis was decreased in only 15 heterozygotes, whereas in the other 11, beta/alpha globin synthesis was in the normal range or was slightly increased. These unusual findings did not appear to be due to the presence of alpha-thalassemia or a hyperactive "normal" beta-allele. This study demonstrates that the beta/alpha ratio of globin synthesis in the peripheral blood is normal in some patients with beta-thalassemia trait. In five Negro homozygotes with relatively mild clinical disease the beta/alpha ratios were similar to those of Caucasians with Cooley's anemia. Further studies are needed to explore the relationship between normal synthesis ratios in many Negro heterozygotes and milder clinical disease in homozygotes in the same families.