In the present study, the levels of fetal hemoglobin (HbF) in sickle cell anemia patients were compared with sickle cell trait, beta thalassemia major and control. The mean HbF levels in beta thalassemia major and sickle cell anemia were 51.62 and 19.63% respectively. However, when the amount of HbF was expressed in terms of gram hemoglobin per deciliter whole blood, the mean values were 2.88 and 1.81 respectively between the two groups, suggesting that the genetic mechanism controlling the different threshold levels of increased HbF in these disorders could probably be similar. The elevated. HbF level in sickle cell anemia along with moderate hematologic profile observed in the present study is suggested to provide amelioration of the clinical severity unlike in beta thalassemia major where despite raised HbF levels, the severe clinical implications are attributed to marked imbalance in the globin chain synthesis. © 1992 Dr. K C Chaudhuri Foundation.