Abstract: Background-Acknowledgement of instrumental action of fetal hemoglobin(HbF) in improving the clinical condition of sickle cell disease (SCD) patients, began around 7 decades back, by Janet Watson who found that infants with SCD had lesser symptoms and their deoxygenated RBCs did not sickle or deform as aggressively as their mothers having sickle cell trait. She proposed high HbF levels in infant blood as compared to mothers for the observations of her study. Reduced incidence of crisis like vaso-occlusive, haemolytic, aplastic, megaloblastic, infectious and others have been found with higher HbF levels. With this backdrop the present study is being undertaken to know the reciprocity between HbF levels and the state of crisis in sickle cell. The study is expected to fill the missing link between “Why a few patients with HbS with haemoglobin pattern of SS suffer less from crisis than that of others with a similar haemoglobin pattern of SS” Objectives: • To know HbF levels in pateints with SCD with Hb (SS) pattern • To draw the comparisons between HbF levels in SCD with Hb(SS) pattern in subjects 1. With sickle cell crisis and 2. Without sickle cell crisis • To find out cut-off level of Hb F at its protective effect against the crisis in SCD Methodology • Study design - Observational and analytical study • Sample size - Total of 30 Patients of sickle cell Disease (Hb SS) • Study duration - 1 year Expected Results: Incidence of Crisis in HbSS patients are expected to have a inverse relationship with HbF levels. A cut-off level of HbF above which episodes of crisis are lower can be expected to be found. Conclusion: Conclusions will be drawn from results obtained and an attempt to establish a cut-off HbF value which renders a protective action against crisis in SCD will be made.