Gene therapy to correct defective genes requires efficient gene delivery and long-term gene expression. The available vector systems have not allowed the simultaneous achievement of both goals. We have developed a chimeric viral vector system that incorporates favorable aspects of both adenoviral and retroviral vectors. Adenoviral vectors induce target cells to function as transient retroviral producer cells in vivo. The progeny retroviral vector particles are then able to stably transduce neighboring cells. In this system, the nonintegrative adenoviral vector is rendered functionally integrative via the intermediate generation of a retroviral producer cell. The chimeric vectors may allow realization of the requisite goals for specific gene-therapy applications. © 1997 Nature Publishing Group.