This study analyzes the effects of individual achievement and achievement level of student reference group on test anxiety in a national sample of 769 gifted Israeli students (grade levels 4Á9), which was previously investigated by Zeidner and Schleyer (1999a). We hypothesized that when controlling for individual achievement, students' experiences of test anxiety should increase with the increasing ability level of their peer reference group. It was assumed that this effect was largely mediated by reference group effects on academic self-concept (big-fish-little-pond effect). Zeidner and Schleyer found that gifted students within a gifted peer reference group showed higher levels of test anxiety than gifted students within a non-gifted peer reference group. Of note, the present study focused exclusively on gifted students attending special gifted classes. The main research question was whether or not the assumed effects of individual and class achievement can be found for gifted students in special gifted classes when taking the variance of achievement level (grades) of the special gifted classes into account. Using hierarchical linear modeling (HLM) methodology, the assumed effects were vindicated for this special group of high ability students. Thus, in line with previous results, the Worry component of test anxiety was more highly reactive to the effects of individual achievement than the Emotionality component. Also, in line with our theoretical assumptions, achievement/anxiety relations were largely mediated by the effects of academic self-concept.Keywords: Test anxiety, worry, emotionality, academic self-concept, achievement, big-fish-little-pond effect, gifted education Numerous studies have investigated the complex pattern of relations between achievement and test anxiety (Zeidner, 2007). Test anxiety has been found to interfere with achievement both in laboratory settings as well as in true-to-real life testing situations in school or collegiate settings (see Zeidner, 1998, for review). While the vast majority of these studies analyzed relations between students' experiences of anxiety and their individual achievement, little research has been conducted on achievement-related peer reference group effects on test anxiety. The present study investigated achievement/test anxiety relations by taking both individual achievement as well as the achievement level of the peer reference group into account. In the next section, we give a brief general description of the nature of the performance/anxiety relationship, and discuss the role of academic self-concept as a