The present invention provides novel methods for enhancing the delivery of transduced cells to a subject, which include both methods of selecting for transduced cells and methods of enhancing the reconstitution by transduced cells in a transplant recipient. The present invention further provides transfer vectors, including lentiviral vectors, useful in practicing the methods of the present invention. The methods and vectors of the present invention may be used in gene therapy of a variety of diseases and disorders, including but not limited to hematological diseases and disorders.