Objective: The objective was to develop and validate an achievement goal scale for young athletes that was aligned with the 2 (mastery/ego) x 2 (approach/avoidance) achievement goal framework. Method: A total of 1675 male and female athletes ranging in age from 9 to 14 years participated in the AGSYS scale development and validation phases. Items having a readability level of grade 4 (age 9) or below were written and evaluated in a series of studies to assess the reliability, factorial validity, and construct validity of the Mastery and Ego scales. Design: Both correlational and experimental methods were used to assess reliability and validity. Results: Exploratory and confirmatory factor analyses demonstrated factorial validity in samples of 9-10-, 11-12-, and 13-14-year-old athletes, and the subscales correlated in a predicted fashion with one another, with other sport and academic goal orientation measures and with several other theoretically relevant variables, including coach-initiated motivational climate, competitive trait anxiety, sport enjoyment, motivation, and self-esteem. Scores also changed significantly in response to a motivational climate coach intervention. Conclusion: The Achievement Goal Scale for Youth Sports (AGSYS) appears to be a reliable and valid measure of achievement goal approach orientations in children between the ages of 9 and 14 years. We were not successful in developing corresponding avoidance goal orientation scales that were not highly correlated, raising the possibility that children do not cognitively differentiate between mastery-avoidance and ego-avoidance orientations. (c) 2007 Elsevier Ltd. All rights reserved.