Human ribosomes obtained from the reticulocytes of patients having either homozygous beta-thalassemia (thalassemia ribosomes) or a hematological disorder unrelated to thalassemia ("normal" ribosomes) have been utilized in a cell-free system highly active in the synthesis of intact human globin chains. This system is dependent on the addition of a ribosomal wash fraction from reticulocytes that contains factors necessary for chain initiation. In response to the ribosomal wash fraction, isolated from either thalassemia, normal human, or rabbit reticulocytes, normal human ribosomes synthesize equal amounts of alpha and beta chains. In contrast, in response to all three types of ribosomal wash fractions, thalassemia ribosomes synthesize 8-times more alpha than beta chains, a ratio similar to that produced in the intact cells of these patients. The molecular defect in beta-thalassemia, therefore, does not appear to be associated with initiation factors.