The first reported case of hemoglobin S and C Harlem in an individual is described. The patient, a 35-yr-old female, had numerous crises during adolescence and early adulthood, but these occurred more infrequently as she grew older. Chemical evidence is presented for the characterization of both variant hemoglobins. The clinical course of this individual with Hb S in combination with Hb C Harlem appears to be similar to that for persons with sickle cell anemia.