Lentivirus has been proved as an excellent gene therapy vector. To date, more than 236 clinical trials have been carried out using lentivirus vectors for gene delivery , and promising gene therapy outcomes from recombinant lentivirus have been achieved from clinical trials for a great number of diseases (Table 1), especially for cancer treatment. As a research tool used to introduce a gene product into in vitro systems or animal models, lentiviral vector has been put into large-scale efforts to down-regulate or up-regulate gene expression in high-throughput formats, allowing researchers to examine the necessity and effects of transgenes in disease model systems, which is an indispensable for the discovery of novel transgenic drugs. To date, lentiviral vector-based gene delivery into CD34+ HSCs has been used as an alternative in clinical trials and proved to be effective in treatment of several diseases , including β-thalassemia , X-linked adrenoleukodystrophy (ALD) , metachromatic leukodystrophy [8,9], and Wiskott-Aldrich Syndrome . Among them, HSCs transduced with β-globin in patients with β-thalassemia, one patient with βE/β0-thalassemia achieved independence from transfusion ; HSCs transduced with wild-type ABCD1 in two patients with X-linked adrenoleukodystrophy (ALD), they achieved polyclonal reconstitution, with 9 to 14% of granulocytes, monocytes, and T and B lymphocytes expressing the ALD protein with the stop of progressive cerebral demyelination ; Functional WASP transduced by lentiviral vector into three WAS patients to genetically correct HSPCs, all the three patients showed improvements in platelet counts, immune functions, and clinical scores . No adverse events related to the vector have been reported in these clinical trials.