AbstractThe origin and course of the nerve to the extensor carpi radialis brevis are closely related to the lateral aspect of the elbow joint and proximal portion of the radius—both of which are frequent sites of pathology and surgical treatment. The specific origin of the nerve supply to the extensor carpi radialis brevis muscle has been attributed variably by diverse anatomic and clinical texts to be the radial nerve, its deep branch or its superficial branch. This study was undertaken to determine the most common source of the nerve to the extensor carpi radialis brevis, as well as the most predictable topographic site of its origin. A total of 111 limbs were dissected, with the most common origin (56.7%) found to be the deep radial nerve, followed by the superficial branch of the radial nerve (31.5%), and least frequently from the bifurcation of the radial nerve into its superficial and deep branches (11.7%). This nerve branch was found to arise in most individuals within one centimeter of the distal edge of the humeroradial joint and to pass distally about 3.5 centimeters before entrance into the extensor carpi radialis brevis muscle. © 1993 Wiley‐Liss,