NCI has conducted a retrospective cohort study with the Maccabi health care Services HMO, which has 2-million enrollees and provides health services to 25% of the total population of Israel. The study assessed different types of fertility medications used within the context of in vitro fertilization to subsequent cancer risk. Investigators obtained medical records on the type of infertility (including male infertility, polycystic ovary disease, endometriosis, structural problems) as well as fertility medications prescribed, and have linked the eligible study population with the Israel Cancer Register. These data allowed investigators to address the relationship between different cancer sites and several medications used in conjunction with in vitro fertilization, while controlling for other cancer risk predictors (e.g., parity).