The analysis is based upon data from a national study of heads of public health programs at the state and local levels. Consistent with Grusky's findings, heads of large public health and of large mental health departments at the State level tend to have shorter tenure than heads of small departments. Although the positions are filled by political appointment, the professional requirements are sufficiently important that the mechanisms discussed by Grusky can operate. Furthermore, the kind of career line, itinerant or home guard, also is relevant; this helps explain the findings that at the local level length of tenure is not inversely related to organization size.