OBJECTIVE: To develop and validate a quality-of-life index for adolescents with skin disease. DESIGN: Prospective, longitudinal cohort study taking place from July 15, 2005, through February 29, 2008. SETTING: Academic pediatric dermatology practice. PATIENTS: A total of 205 patients between the ages of 12 and 17 years with a skin condition. MAIN OUTCOME MEASURES: Participants completed the Skindex-Teen questionnaire, reported sociodemographic data, and answered clinical questions at enrollment. Four weeks later, they completed Skindex-Teen and responded to clinical questions again. Forty patients also completed Skindex-Teen 48 hours after baseline. RESULTS: Of 205 patients, 200 (97.6%) completed all enrollment materials; 125 (62.5%) of these returned follow-up materials, of which 115 (57.5%) were complete. Twenty-three of 40 participants (57.5%) completed the 48-hour-after-initial-answers materials. The mean (SD) age of the patients was 15.3 (1.4) years (range, 12.9-18.0 years). Approximately half reported their skin condition as poor (26 [13.0%]) or fair (67 [33.5%]); most rated their general health as very good (62 [31.0%]) or excellent (80 [40.0%]). The dimensionality of the items was evaluated using factor analysis; results suggested 2 factors, termed physical symptoms (5 items) and psychosocial functioning (16 items). Both scales demonstrated excellent internal consistency. All item-scale reliabilities were greater than 0.4. Fit of items to the measurement model was supported by Rasch analysis. Test-retest reliability was supported by intraclass correlation coefficients (0.82-0.94) for total scores, physical symptoms, and psychosocial functioning scales. At 4 weeks, 16 (13.9%) reported worsening of their skin condition, 57 (19.6%) reported it had remained unchanged, and 42 (36.5%) reported improvement. Significant mean differences were present between the improved and worsened groups for the psychosocial functioning scale and total scores. CONCLUSIONS: These data provide evidence of construct, content, and face validity for Skindex-Teen, a new quality-of-life instrument for adolescents with skin disease. Test-retest reliability was verified, and responsiveness at 4 weeks was shown for total scores and the psychosocial functioning scale scores.