Self-determination theory provides an integrated conception of school- and academic motivation. The theory proposes a continuum comprising three types of motivation: intrinsic motivation (IM), extrinsic motivation (EM), and amotivation (AM), characterised by seven dimensions (IM = to know, to accomplish and to experience stimulation, EM = external regulation, introjection and identification, and Amotivation). The purpose of the present study was to examine the psychometric properties of the Academic Motivation Scale (AMS) with Greek high school students. Two studies were conducted to examine the factorial, construct, concurrent and predictive validity of the scale along with its reliability properties. Confirmatory factor analyses supported the proposed seven-factor structure. The scale showed satisfactory levels of internal consistency and temporal stability. Additionally, indices of the scale's construct, concurrent, and predictive validity were in the desired direction. These findings support the use of the Greek version of the AMS for the assessment of intrinsic motivation, extrinsic motivation, and amotivation. (Contains 4 tables, 1 figure and 1 note.)