The outcome of a project is shaped by the output of the project’s team, whose performance is in turn influenced by the project manager’s leadership style. This article examines the results of a field study on how a project manager’s leadership style affects a project’s outcome, one focused on identifying the leadership style that may optimize a project team’s performance. In doing so, it discusses the problems that project managers face when attempting to gain the support of their project teams; it defines five types of interpersonal influences that project managers can use to lead project teams. It then analyzes the results of a survey administered to 88 project professionals and examining three areas of project leadership: degree of support, influence bases, and the relationship between these two areas. It also explains how project personnel perceived the impact of the support they gave to their project manager and to other project managers and how project managers perceived the impact of the support they received from their project team and from other interface personnel. It concludes by identifying the factor that most encourages–and the factors which least influence–project personnel to support project managers, suggesting as it does how project managers can most effectively stimulate project team support.