Globin-chain synthesis was studied in the peripheral blood and bone marrow of eight beta-thalassemia heterozygotes. Whole cell globin was prepared immediately after the labeling experiment. Chain separation of the bone marrow globin of each case was carried out with both the original material and after filtration on Sephadex G 100. The beta/alpha ratios obtained were (mean +/- SD): 0.46 +/- 0.05 in the peripheral blood, 0.61 +/- 0.06 in the unfiltered bone marrow globin, and 0.52 +/- 0.05 in the bone marrow globin after gel filtration. The results show that beta-thalassemia heterozygotes have a similar beta-chain deficiency in reticulocytes and bone marrow cells, provided whole cell globin is used, which avoids the removal of free alpha-chains.