A new scoring system-the sulcus score-was developed to differentiate between a large superior labral sulcus and a type II superior labrum anterior-posterior (SLAP) lesion. The sulcus scoring system permits quantification of the size of the superior labral sulcus and the severity of a type II SLAP lesion. Specifically, the depth of the superior labral sulcus was classified into 4 grades, and the length was recorded by clock position. The sulcus score was then calculated by multiplying the depth (grade) by the length (the number of "hours" from the clock position). After stretching of the anterior capsule into excessive humeral external rotation at 60 degrees glenohumeral abduction, the sulcus score of cadaveric shoulders increased significantly (before, 3.4; after, 6.8), indicating the extension of the superior labral sulcus and resulting in a pathologically created type II SLAP lesion. The intraclass correlation coefficient and mean difference were 0.77 and 0.8 +/- 0.7, respectively, for intraobserver repeatability and 0.72 and 0.9 +/- 0.6, respectively, for interobserver reproducibility. The sulcus score provided a consistent and objective means for quantitatively describing the size and severity of type II SLAP lesions. Clinical assessment of the superior labral sulcus by use of the sulcus score may be useful for the diagnosis and treatment of type II SLAP lesions.