Retroviral vectors have been central components in many studies leading to human gene therapy. However, the generally low titers and inefficient infectivity of retroviral vectors in human cells have limited their use. We previously reported that the G protein of vesicular stomatitis virus can serve as the exclusive envelope protein component for one specific retroviral vector, LGRNL, that expresses vesicular stomatitis virus G. We now report a more useful general transient transfection scheme for producing very high-titer vesicular stomatitis virus G-enveloped pseudotypes from any Moloney murine leukemia-based retroviral vector without having to rely on the expression of the cytotoxic G protein from the retroviral vector itself. We also demonstrate very high efficiency of infection with a pseudotyped lacZ vector in primary mouse hepatocytes. We suggest that pseudotyped retroviral vectors carrying reporter genes will permit genetic studies in many previously inaccessible vertebrate and invertebrate systems. Furthermore, because these vectors represent retroviral vectors of sufficiently high titer to allow efficient direct retroviral-mediated in vivo gene transfer, we also suggest that pseudotyped vectors carrying potentially therapeutic genes will become useful to test the potential for in vivo gene therapy.