Narrative Title: Paternal Environmental Exposures and Reproductive Outcomes: A Comparison of in vitro and in vivo Fertilization At this writing, 900 children with Spina Bifida of Agent Orange exposed Vietnam veterans receive VA presumptive service connected benefits. This underscores the pressing need to explore the intersection of paternal environmental exposures and birth outcomes and corresponds to the expectations of the Agent Orange Act of 1991 (Public Law 102-4) that new scientific information related to the exposures will be generated. This study design is unique in its ability to: a) characterize the impact of the exposure to seminal fluid during in vivo fertilization on the reproductive outcomes resulting from mating with either Dioxin exposed or non exposed males, b) address reproductive outcomes following paternal preconception exposure in the absence of maternal seminal fluid contact through the process of in vitro fertilization, and c) provide evidence for deleterious effects on developing gametes during the process of spermatogenesis. Through the identification of potential biologic mechanisms, progress can be made in the prevention of future adverse reproductive outcomes that result from male preconception exposure to environmental agents, a concern that continues for Gulf War I veterans and OEF/OIF veterans and military personnel today