A simplified method for generating recombinant adenovirus was developed by using liposome-mediated co-transfection and by directly observing for the cytopathic effect caused by recombinant adenovirus in transfected 293 cells. This approach avoided difficulties associated with calcium-phosphate precipitation and agarose overlays for plaque assays. The ease of generating recombinant adenovirus was considerably improved. Analysis by PCR of DNA samples from the supernatant of the cell cultures with the cytopathic effect was also developed, which made identification of any newly generated recombinant virus rapid and specific.