Gene therapy is a new therapeutic modality with the potential of treating inherited and acquired diseases. Several viral and physicochemical vehicles have been used for the transfer of genes to mammalian cells, but recombinant retroviruses are used in the majority of gene therapy clinical trials today. In this communication, we review the major concerns associated with the large-scale production and processing of retroviral particles. While some of the current processes for manufacturing recombinant proteins will be applicable to recombinant retroviruses, the instability, sensitivity to inhibitors, complexity, and size of retroviral particles require that new technologies be designed and evaluated. Here, we examine those issues critical to the design of strategies for production, concentration, and purification as well as formulation and storage of recombinant retroviruses. Processes for large-scale manufacturing of recombinant retroviruses that can produce high gene transfer efficiencies will have significant impact on the clinical implementation of gene therapy.