A method is provided for genetically modifying primate bone marrow cells, comprising isolating bone marrow cells from a primate and, by means which enhance the local concentration of retroviral contacting the isolated bone marrow cells to cells that produce a recombinant amphotropic retrovirus with a genome based on a retroviral vector that contains the genetic information to be introduced into the bone marrow cells. Recombinant amphotropic retrovirus-producing cells, suitable for use in this method also are provided, as are genetically modified primate bone marrow cells with the capacity for regeneration in vivo.