Evidence on the cost-effectiveness of physician assistants has accumulated in diverse sources in recent years. In this analysis the findings of major studies which bear on the issue are assembled and evaluated. Numerous studies indicate that the utilization of physician assistants has a positive correlation with productivity measures; other studies reveal significant cost savings as well. This conclusion has several important qualifications and implications: (1) the generality of physician assistants cost-effectiveness has not yet been demonstrated; (2) patients and third parties may not benefit so that physician assistants may serve only in increase physician incomes, which may reduce patient acceptance and affect overall utilization rates of physician assistants; and (3) reimbursement policies are inadequate and may curtail cost-effective utilization of physician assistants in many circumstances.