A total of 75 (45 males, 30 females) patients with sickle cell disease (SCD) at the university of Maiduguri Teaching Hospital were screened for G-6-PD deficiency and their steady state levels of haematocrit, reticulocyte count and irreversibly sickled cells (ISC) as well as the occurrence of vaso-occlusive crises were analysed with respect to their G-6-PD status during a 3 year period (1998-2000). None of the female patients was G-6-PD deficient, while (15.6%) male patients had the enzyme deficiency. The patients with G-6-PD deficiency had significantly lower mean level of haematocrit (0.221/l) with higher level of reticulocyte count (15%) as compared to their non-G-6-PD deficient counter parts who had mean values of 0.271/l and 9% for haematocrit count respectively. However, there was no significant difference in mean levels of ISC between G-6-PD deficient (6%) and non-G-6-PD deficient (5%) patients with SCD. Patients with G-6-PD deficiency had significantly lower episodes of vaso-occlusive crises (2.1 episodes/patient). This data would suggest that co-inheritance of G-6-PD deficiency in SCD reduces frequency of crises and improves prognosis.