The red cell distribution width index (RDW) and other cell indices (HCT, MCV, MCH) were determined in 171 normal infants and children, 37 patients with sickle cell disease (SCD) and 44 patients with sickle cell trait (SCT). The red blood cell indices including RDW in normal children showed a significant difference between different age groups (P < 0.01), while in different sex groups, they did not differ significantly. SCD group showed a significant increase in RDW and a significant decrease in the hematocrit (HCT) value when compared either with the control or the SCT groups (P < 0.01). Patients with SCD showed a significant increase in their RDW and a significant decrease in their hematocrit values during haemolytic crises as compared with those during vaso-occlusive crises (P < 0.01). A positive linear correlation between RDW and the reticulocyte count in SCD and SCT patients. (r = .8842, P < 0.01) was also found. In this context it was concluded that RWD values do reflect the reticulocytes magnitude which would provide clinical and pathological information about SCD and its crises.