The delivery of psychological services has become more differentiated and more specialized over the last three decades. The newest, and perhaps potentially most significant, direction for psychology is the drive toward prescriptive authority for appropriately trained licensed psychologists. This direction is more an outcome of the overall changes in the role of psychology in health care than a particular usurpation of medical turf. The authors present a retrospective review of the trajectories for psychiatry and psychology that have focused psychology on prescriptive authority. A prospective indication of the emerging models of practice is described, illustrated by the limited anecdotal data currently in the literature and professional presentation venues.