Ovarian cancer is the deadliest gynecologic cancer. Unlike many cancers such as breast, cervical and colon cancers, there is no easily clinically identifiable pre-malignant phase of this malignancy making early identification difficult. Similarly, unlike lung, head and neck, and skin cancers, there is not easily identifiable risk factor making prevention short of oophorectomy difficult. Even so, theories as to the causative factors of ovarian cancer continue to evolve making our understanding of the genesis of ovarian cancer more clear. Genetics, parity, environment, hormonal factors, and inflammation all play an important and pivotal role in the development of ovarian cancer. The most current understanding of these elements and their respective contribution to the development of this cancer are presented in this chapter.