Current and future demands of viral vectors for the development of successful pre-clinical and clinical studies in human gene therapy and possible commercialization of gene therapy products require well-established large-scale production processes. One of the most promising vectors for human gene therapy is recombinant adeno-associated virus vectors (rAAVs). Some of the attractive features of rAAV are broad tissue tropism, low immunogenicity, ability to transduce both mitotic and post-mitotic cells, and long-term gene expression in non-dividing cells. Recently, we developed a novel technology for the production of these vectors exploiting baculovirus expression vectors (BEV: ) in insect cell cultures. Initially developed in small, shake flask format, this process has been successfully scaled to larger volumes. In an effort to standardize rAAV production in stirred tank bioreactors, we characterized the culture conditions to derive a set of parameters correlated with high rAAV yields. Measuring capacitance and dielectric spectroscopy with a permittivity probe enabled us to determine optimal times of infection and harvest. Consistent yields of rAAV, 2 x 10(13) DNase-resistant vector genomes (vg) [1 x 10(12) transducing units (tu)] per liter of cell culture were obtained in bioreactors with working volumes ranging from 10 to 40 l. This represents significant progress toward establishing a robust large-scale process at industry level.