The purpose of this study was to examine the psychometric properties of the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES), patient self-report section. Patients with shoulder dysfunction (n = 63) completed the ASES, The University of Pennsylvania Shoulder Score, and the Short Form-36 during the initial evaluation, 24 to 72 hours after the initial visit, and after 3 to 4 weeks of physical therapy. The test-retest reliability (intraclass correlation coefficient[1-way random-effects], 0.84; 95% CI lower limit, 0.75) and internal consistency (Cronbach alpha, 0.86) values were acceptable. The standard error of the measure was 6.7 ASES points (90% CI, 11.0). Construct and discriminant validity was demonstrated. Responsiveness was demonstrated with a standardized response mean of 1.5 and an effect size of 1.4. The minimal detectable change was 9.7 ASES points (90% CI, 16), and the minimal clinically important difference was 6.4 ASES points. The results indicate that the ASES is a reliable, valid, and responsive outcome tool.