Sickle cell trait is present in about 8% of black Americans, and clinically significant sickling disorders are common in this population. These disorders can be accurately defined by combinations of quantitative hemoglobin electrophoresis at alkaline pH, citrate agar electrophoresis, solubility tests for sickle hemoglobin, fetal hemoglobin measurements, blood counts, erythrocyte indices and family studies. Unusual types of sickling hemoglobinopathies may require more extensive, specialized study. An unquestioned diagnosis should be prerequisite for any subsequent genetic counseling.