Sickle cell anemia exhibits significant variations in clinical presentation in different populations despite the homogeneity of the genetic defect which is involved. Genetic modulation of this disease is known but cannot explain alone such observations. Our objectives were to determine the effects of Hb F level, sociocultural and economic factors on disease severity in Dakar. Sixty homozygous sickle cell patients were followed up between october 1996 and April 1998 during which period the severity of the disease was assessed and a "severity index" was calculated for each patient. The factors which were identified with proved benefit were: Hb F > 15%, a high socioeconomic level, a good understanding of the disease, at least 4 medical visits per year. These results allow us to identify some potential targets to improve preventive and curative care of this disease.