For the past two decades, scientists have aggressively pursued the development of a vaccine against human immunodeficiency virus (HIV). The magnitude of this effort is unprecedented in the history of infectious diseases. However, difficulties in finding promising candidate vaccines have limited the number of clinical efficacy trials. The macaque model is well suited for the evaluation of potential vaccines, but comparison of results among studies is often complicated by the use of different macaque species and/or challenge viruses. This review discusses current results obtained in the macaque model and human vaccine trials.