This chapter provides a comprehensive overview of upper extremity arterial anatomy, which is essential for successful distal radial access procedures. It describes the course and relationships of the axillary, brachial, and radial arteries, with particular emphasis on the radial artery’s path through the anatomical snuffbox. The chapter examines common anatomical variants and presents the ABC classification system for identifying and managing these variants. The clinical implications of these variants, including their impact on procedural success rates and potential complications, are also discussed. Group A variants relate to the radial-brachial axis, Group B involves the axillary-subclavian axis, and Group C concerns aortic arch variants. Each group presents unique challenges that require specific management strategies. By mastering this anatomical knowledge, interventionalists can better anticipate and manage potential difficulties, optimize procedural techniques, and improve distal radial access procedures.