Endometriosis is a complex gynecologic disorder that affects as many as 10-15% of premenopausal women. Epidemiologic studies have confirmed that this disease is a genetic disorder of polygenic/multifactorial inheritance. The disorder has long been recognized to show heritable tendencies with recurrence risks of 5-7% for first-degree relatives. The current investigational goal is to determine the number and location of causative genes, a process that has been made possible by recent advances in molecular technology. This chapter discusses heritability studies supporting polygenic/multifactorial inheritance, the scientific basis of genome-wide strategies for identifying causative genes and potential candidate genes.