Increased levels of red cell fetal hemogloblin, whether due to hereditary persistence of expression or from induction with hydroxyurea therapy, effectively ameliorate sickle cell disease (SCD). Therefore, we developed erythroid-specific, gamma-globin lentiviral vectors for hematopoietic stem cell (HSC)-targeted gene therapy with the goal of permanently increasing fetal hemoglobin (HbF) production in sickle red cells. We evaluated two different gamma-globin lentiviral vectors for therapeutic efficacy in the BERK sickle cell mouse model. The first vector, V5, contained the gamma-globin gene driven by 3.1 kb of beta-globin regulatory sequences and a 130-bp beta-globin promoter. The second vector, V5m3, was identical except that the gamma-globin 3'-untranslated region (3'-UTR) was replaced with the beta-globin 3'-UTR. Adult erythroid cells have beta-globin mRNA 3'-UTR-binding proteins that enhance beta-globin mRNA stability and we postulated this design might enhance gamma-globin expression. Stem cell gene transfer was efficient and nearly all red cells in transplanted mice expressed human gamma-globin. Both vectors demonstrated efficacy in disease correction, with the V5m3 vector producing a higher level of gamma-globin mRNA which was associated with high-level correction of anemia and secondary organ pathology. These data support the rationale for a gene therapy approach to SCD by permanently enhancing HbF using a gamma-globin lentiviral vector.