This study explored academic underachievement of fourth form boys in male secondary schools within the Auckland area. There were two aspects to this study; firstly, to identify students who are underachieving relative to their abilities and secondly, to explore possible psychological differences between underachievers and non-underachievers. An underachiever for the purpose of this study is a student who is achieving lower grades than expected in accordance with his abilities (McCall, Evahn & Kratzer, 1992). 598 of the 770 students enrolled in the participating schools had the necessary data for regression analyses to identify underachievers. Of the 598 students with valid data, 315 consented to participate in the questionnaire. The sample for this study comprised 315 fourth form boys. A discrepancy model using regression analysis was carried out on the 315 students to identify underachievers within the schools. 82 students were identified as underachievers using this method, which resulted in 13.9% of the sample being defined as underachievers. In addition, a self-report questionnaire was administered to the 770 students. The questionnaire measured six psychological dimensions that have been identified in previous research to be related to academic achievement. The responses of the underachieves and non-underachievers were compared to ascertain whether these two groups differ on the psychological dimensions measured. These psychological constructs measured in the questionnaire included study strategies (cognitive/self-regulation, persistence/effort, and disorganisation), social support, self- efficacy, test anxiety, intrinsic motivation/interest in school subjects, and outcome expectancies. There was a significant mean difference between non-underachievers and underachievers on the disorganisation scale. This finding suggests that underachievers had more disorganised study habits than their non-underachieving comparison group. There were also significant mean differences between underachievers and non-underachievers for intrinsic value in English and science. These findings suggested that underachievers were more intrinsically motivated in English than their non-underachieving comparison group, but less intrinsically motivated in Science.