The Halley Consulting Group is a physician practice management and consulting firm specializing in the strategic development and performance turnaround of both hospital-owned medical practice networks and large independent medical offices. The firm was originally organized in 1995 as Ambulatory Management Services, Inc. (AMS), a subsidiary of Holy Cross Health System Corporation, to meet the needs of its member hospitals nationally. Following the merger of Holy Cross and Mercy Health Services in 2000, AMS became a wholly owned for-profit subsidiary of Trinity Health, Novi, Michigan. In 2005, AMS became The Halley Consulting Group, LLC, a privately held company. The firm is headquartered in a suburb of Columbus, Ohio. Halley Consulting works with clients nationwide, including health systems and individual hospitals that own medical practice networks, as well as private practice physicians. They provide services through traditional consulting arrangements and interim management contracts. The firm has served physician groups as small as 10 providers and health systems with up to 800 providers of varying specialties all across the United States. Hospital-owned networks employing several hundred providers use the Halley Consulting financial and statistical model as the basis for their management decisions and performance improvement efforts.