The adeno-associated virus 2 (AAV) genome can be rescued either from a recombinant plasmid upon transfection into human cells or from cells latently infected with AAV, following subsequent infection with adenovirus. Using human diploid fibroblasts as a model for a natural AAV infection, we observed increased efficiency of rescue of the AAV genome in these cells as they traversed their limited proliferative life span in vitro. The efficiency of rescue correlated well with the augmented nuclease activity in these cells. Furthermore, rescue of the AAV genome, either from a recombinant plasmid or from the chromosomal DNA, was more efficient in cells from a patient with Bloom’s syndrome, a rare autosomal recessive disease associated with increased chromosomal breakage due to DNA ligase I deficiency, as compared with normal human diploid fibroblasts. These studies suggest that alterations in DNA-modifying enzymes may play a role in rescue of the AAV genome in human cell