The process of defining underachievement, identifying underachieving gifted students, and explaining the reasons for this underachievement continues to stir controversy among practitioners, researchers, and clinicians. Despite this interest, the underachievement of gifted students remains an enigma. This article reviews and analysis three decades of research on the underachievement of gifted students in an attempt to clarify the present state of research. The problems inherent in defining and identifying underachieving gifted students are given special attention. The authors also include suggestions for those interested in pursuing potentially promising new lines of research and inquiry in this area.