A slow-moving hemoglobin with electrophoretic mobility similar to that of hemoglobin S was discovered in a white laboratory technologist. She had an elevated reticulocyte count, as did several members of her family. Her red cell survival was shortened. Amino acid analysis indicated that leucine at position β48 (CD7) had been replaced by arginine. The abnormal hemoglobin, called Okaloosa, was heat-precipitable and had decreased oxygen affinity. It exhibited a greater change in oxygen affinity than hemoglobin A when 2,3 DPG was added to “stripped” hemolysates. These findings cannot be readily explained by current views of structure-function relationships in the hemoglobin molecule. However, it is of interest that the amino acid in position CD7 is normally leucine in the α, β, δ, and γ-hemoglobin chains and in the myoglobin chain of man and a wide variety of other vertebrates.