Since its original description in 1963, the pregnancy luteoma has been a controversial entity both clinically and pathologically. The most important questions which have been asked are: Is the luteoma a true neoplasm or does it represent simply an abnormal response to the hormones of pregnancy? What is the relation between the tumor and certain endocrinopatheies that are associated with these lesions? This study of 20 cases collected from the flies of the Emil Novak Ovarian Tumor Registry and the Pathology Section of the Baltimore City Hospitals directs its attention to these critical clinicopathologic features.