Hematologic evaluation of a Nigerian obstetrical patient disclosed the presence of sickle-cell trait as well as evidence of a hemoglobin alpha- chain abnormality. Hemoglobins containing the variant alpha-chain were isolated by DEAE-cellulose column chromatography, and analysis of the purified alpha-chain demonstrated a ser replaced by cys substitution at alpha-81. The abnormal alpha-chain represented approximately 45% of the total, and hemoglobins containing this alpha-chain appeared to have normal stability and functional properties. In addition to the abnormal hemoglobins that were identified in this patient, she also was found to have persistent microcytosis in the absence of iron deficiency, and the percentage of HbS in her erythrocytes was less than that usually present in individuals with sickle cell trait. These findings, together with a reduced alpha/beta globin synthesis ratio from her peripheral blood reticulocytes, indicated that the presence of alpha-thalassemia trait. Hematologic findings from members of the patients's family suggest that an alpha-thalassemia gene may be linked to that of the structurally abnormal alpha-chain.