The most superior part of the superficial layer of the supinator muscle is named as the arcade of Frohse (AF). The deep branch of the radial nerve runs under this arch. The AF is reported to be the most common structure causing entrapment neuropathy of the deep branch of the radial nerve. The aim of our study was to reveal the anatomical properties and especially morphometric measurements of the AF in cadavers. This study was performed on 55 cadaver upper extremities. The AF was classified macroscopically as either tendinous or membranous. The width, length and thickness of the AF were measured as the dimensions of the AF. The "distance AF" between the lateral epicondyle of the humerus and the AF was measured. The "forearm length" between the lateral epicondyle of the humerus and the styloid process of the radius was measured. The distance AF was divided by the forearm length to find the "ratio AF". In 87% of the extremities the AF was tendinous, and in 13% it was membranous. The mean width, length and thickness of the AF were 10.13, 8.60 and 0.77 mm, respectively. The mean distance AF and forearm length were 46.23 and 233.17 mm, respectively. The mean ratio AF was 0.199 (approximately 1/5). These measurements of the dimensions of the AF may contribute to the anatomy of the AF. The surgeon may find the predicted distance AF of any upper extremity by dividing its forearm length by 5.