The Interlocking Directorates Handbook on Section 8 of the Clayton Act provides history, background, and practical guidance on the application of Section 8 of the Clayton Act, which regulates "corporate interlocks"—where two competing corporations share one or more directors in common. This handbook provides a concise history of Section 8, discusses common procedural issues that arise in litigation involving Section 8 claims, summarizes the interplay between Section 8 and other regulatory schemes, and finally, discusses practical guidance and common pitfalls for practitioners. Today, Section 8 is an important issue to the modern corporation. Indeed, with the increased activity of private investment funds, many of which take multiple board seats in addition to their equity positions, Section 8 issues have become more widespread. In addition, as technology companies expand their product reaches into new areas, companies that previously did not compete have been confronted with Section 8 issues. This handbook will serve as a useful reference to any antitrust practitioners advising corporations and investment funds.