Underachievement has long been recognised as a problem for some gifted children. The aim of the research described in this article was to investigate the affective characteristics of achieving and underachieving intellectually gifted children. In particular, the three affective characteristics were academic self-concept, self-expectations for future achievement and academic locus of control for children who were moving from elementary school to a middle school setting. Forty- one participants were chosen who had a Full WISC-R test over 125 from a large sample of middle school-aged children entering Middle School in a New Zealand city. Of these 41 intellectually gifted participants, 7 were classified into an underachieving group as a result of their scores on a Performance Achievement Test. The remaining 34 were classified into an achieving gifted group. A third group, classified as average achievers, was composed of students who had average WISC-R FS IQs and whose achievement test scores were also average. The results indicated that the most discriminating construct between the groups was self-expectations for future achievement. The discussion focuses on appropriate remediation and on how newer areas of motivation, self- regulation and goal orientations may be more appropriate constructs to discriminate this group of learners.