Of 18 nonblack patients with sickle cell disease, 14 had sickle cell anemia, 2 had hemoglobin SC disease, and 2 had hemoglobin S-beta o-thalassemia. The beta s gene cluster haplotypes that were determined in 7 patients were of African origin and were identified as Central African Republic, Central African Republic minor II, Benin, and Senegal. The haplotype Central African Republic minor II was present on the beta o-thalassemia chromosome in 2 patients. None of 10 patients whose alpha-gene status was determined had alpha-thalassemia-2. These data strongly support the concept that the beta s gene on chromosome 11 of these individuals is of African origin and that the alpha-gene locus on chromosome 16 is of white or native American origin. The clinical severity of the disease in these nonblack patients is appropriate to their haplotype without alpha-thalassemia-2 and is comparable with that of black patients. All persons with congenital hemolytic anemia should be examined for the presence of sickle cell disease regardless of physical appearance or ethnic background.