Sickle cell trait (SCT) affects approximately 8% of the population in Martinique (FWI) and about the same rate is found among the African Americans. In several regions of tropical Africa, up to 40% of individuals are also affected. SCT has been characterized as a benign condition and patients are currently asymptomatic or run a benign course. However, life-threatening complications may occur. SCT can be detected in patients hospitalized for various complaints, and SCT likely causes serious morbidity and mortality in some people. Moreover, these clinical observations have been supported by several in vitro studies in which haemoglobin AS red cells showed abnormalities of their filterability. These problems are revisited with the implementation of universal leucoreduction in several countries. The question of the screening of all blood donors for SCT and the use of their red blood cells (RBCs) has yet to be resolved.