In much of the country a corporation may not own a medical practice, and yet corporations effectively run thousands of them. This article explains how that happened and what the law actually requires. It covers the corporate practice of medicine doctrine and where it came from, the professional entity forms that satisfy it, and the management services structure that has grown up around it. It explains fee splitting prohibitions and why they constrain compensation arrangements that look ordinary in any other industry, and it works through the anti-kickback and physician self-referral statutes that overlay everything in health care. It covers what buyers actually diligence in a practice acquisition, the restrictive covenants that follow professionals across employers, and the antitrust and licensing constraints on professional self-regulation. It closes with what goes wrong and how these structures are unwound.