As increasing numbers of female physicians enter the specialty of obstetrics and gynecology, their productivity (defined as producing goods and services) as compared with male physicians becomes important. Data from the American Medical Association socioeconomic survey and from a survey of ACOG Fellows indicate that, as a group, female physicians in the specialty are approximately 85% as productive as male physicians in the specialty. ACOG data for physician net income validate the productivity calculations (P <.03). The increasing numbers of female physicians in the specialty will lead to a decreasing aggregate productivity. At the same time, the increasing numbers of women of all ages in the United States will lead to a decline in the available obstetrician-gynecologist work force beginning in the year 2010.