Lentiviral vectors (LVs) are the most recently developed viral-derived vectors for gene therapy applications, and have demonstrated much promise. The ability to transduce dividing and non-dividing cells, and sustain long-term transgene expression makes LVs uniquely desirable as gene therapy vectors. With advances in vector design and large-scale production, LVs have become safer and more effective gene delivery systems. Since the first clinical trial was approved in 2002, several trials to treat patients with both infectious and genetic diseases have been approved. This review focuses on ongoing and planned trials of LV-based gene therapy.