The aim of this study was to determine the reliability, validity, and sensitivity of the Patient-rated Tennis Elbow Evaluation (PRTEE) Questionnaire in 78 tennis playing subjects who had chronic, unilateral, MRI-confirmed lateral elbow tendinopathy and who concomitantly participated in an outcome study. The PRTEE results were compared with results of the Visual Analog Scale (VAS); the Disabilities of the Arm, Shoulder, and Hand (DASH) Questionnaire; the Roles and Maudsley score; and the Upper Extremity Function Scale. Questionnaires were completed at baseline and 12 weeks. Reliability and internal consistency were excellent (PRTEE pain subscale, 0.94; PRTEE specific activities subscale, 0.93; PRTEE usual activities, 0.85). Correlations were good between the PRTEE subscales and total scale and the VAS and DASH. Standardized response means (SRM) were higher in the PRTEE (SRM=2.1) than in the other outcome measures (SRM, 1.5-1.7). The PRTEE was a reliable, reproducible, and sensitive instrument for assessment of chronic lateral elbow tendinopathy in a tennis playing cohort. It was at least as sensitive to change as the other outcome tools tested. The PRTEE may become the standard primary outcome measure in research of tennis elbow.