Endometriosis is inherited in polygenic/multifactorial fashion, with recurrence risks of 5-7% for first-degree relatives. The current task is to determine the number and location of causative genes. This review initially supports the basis for polygenic/multifactorial inheritance and then outlines genome-wide strategies for identifying causative genes. Potential candidate genes are surveyed, and discrepant results emphasized. Finally, a hypothesis for endometriosis, having a multi-step pathogenesis analogous to the pathogenesis of neoplasia, is considered.