Interim directorships are an important, but little investigated, aspect of museum management. This study of 52 interim directorships in the United States provides baseline parameters of the experience: how long it lasts, who is selected to serve, and how the experience affects their careers. One-fifth of the interim appointees assume the directorship in their museums, including nearly one-half of those who actively sought the position and one-fifth leave the institution shortly after their interim experience. Interim directorships appear to be an indicator of future museum appointments, as one-third of the interim appointees went on to regular directorship appointments later in their careers. This paper argues that the appointment of internal candidates as interim directors significantly alters the social ecology of the museum. It also discusses the ethical issues represented by the appointment of interim directors and suggests areas for further research.