This study employed an experimental design to assess the effectiveness of supervisor training conducted by a large corporate employee assistance program (EAP). A total of 291 supervisors were randomly assigned to one of three study groups, and data were collected immediately following the training sessions. Supervisor training conducted by both in-house and contracted EAP trainers was found to be effective. In addition, these data demonstrate that supervisor training is best viewed as a process and not as a single event. Additional training had a significant impact on supervisors' knowledge of the EAP even after controlling for previous training and previous experience with the EAP.