A reduction in the height of the suprascapular foramen may predispose to entrapment of the suprascapular nerve. In this study, 16 of 27 cadavers (60%) demonstrated a heretofore unreported ligament located on the anterior aspect of the suprascapular foramen. In 11 of the 27 cadavers (41%), the ligament was observed bilaterally. The ligament decreased the foraminal height from the normative value of 5.6 +/- 0.4 to 2.3 +/- 0.4 mm (mean +/- SEM). Because this ligament, for which we propose the term anterior coracoscapular ligament (ACSL), substantially narrows the suprascapular foramen, it should be considered as a possible etiologic factor in suprascapular nerve entrapment.