Reproductive toxicology is relatively new to the field of gene therapy, and is a very important issue for the safety. An important safety concern of gene therapy products is the distribution of vector beyond target organs. This is particularly important if vector distributes to gonads, raising the possibility of inadvertent germ-line transmission. In addition, for indications such as prostate cancer and ovarian cancer, the proximity of the point of viral administration to organs of the reproductive system raises concerns regarding inadvertent germ-line transmission of genes carried by the virus. To evaluate the reproductive toxicity of in vivo El-deleted replication-incompetent adenoviral vector encoding p53 or lacZ, we studied the biodistribution and potential germ-line transmission of the vector. Both male and female Balb/c mice were injected with $1{ imes}10^8;pfu$ of Ad-CMV-LacZ or Ad-CMV-p53. DNA and RNA extracted from major organs including gonadal tissues were analyzed for vector sequences and expression. The PCR analysis showed that there were detectable vector sequences in liver, kidney, spleen, seminal vesicle, epididymis, prostate, ovary, and uterus. The RT-PCR analysis showed that Ad-CMV-LacZ or Ad-CMV-p53 viral RNA were present in spleen, prostate and ovary. Vector-administered female and male mice were mated and their offspring were evaluated for germ-line transmission of the adenoviral vector. The PCR analysis showed no evidence of germ-line transmission, although vector sequences were detected in DNA extracted from gonadal tissues. Together, we conclude that the risk of the inadvertent germ-line transmission of vector sequences following intraperitoneal injection of adenovirus is extremely low, although vector distributed to gonadal tissues.