Objectives. To explore differences in the appointment and election method of selecting state high court justices in promoting gender diversity, and to explore the effect of existing gender diversity within the political institutions on the selection of women to office. Methods. Our data include all justices who have been selected to state courts of last resort from 1980 through 1997. We use logistic regression analysis to test the effect of existing gender diversity on a high court on the likelihood that a woman will be selected to fill a vacancy. Results. Women are significantly more likely to be selected to a state high court when initially appointed, and this effect is particularly pronounced when the governor is Democratic. When an appointment system is used, women are much more likely to be appointed to an allmale court than to a gender-diverse court. Conclusions. Appointment systems are more likely to create gender diversity on state courts; however, this effect operates primarily to diversify all-male courts. This difference between appointment and election systems may reflect differences in knowledge between elite actors and the mass public about the composition of the institution.A variety of arguments have been offered for the promotion of gender diversity within government. The foundation of many arguments for increased diversity is the belief that, regardless of whether because of biological, psychological, or sociological differences, women bring a different set of attitudes and beliefs and different areas of experience and expertise to policy making (Darcy, Welch, and Clark, 1994;Sapiro, 1981). Those who advocate diversity within government frequently argue that overwhelmingly male political institutions do not adequately represent the diverse interests of the mass