Binge eating disorder (BED) is a syndrome marked by recurrent episodes of binge eating, in the absence of the regular use of inappropriate compensatory behaviors. Since the inclusion of BED in DSM-IV as a Diagnostic Category in Need of Further Research, a great deal of research has been conducted. This paper reviews research on BED since publication of DSM-IV in 1994. We conclude that questions about the definition of BED persist. Furthermore, recent studies which have strictly used the DSM-IV definition of BED have found that the full syndrome is found in less than 3% of obese adults seeking weight loss treatment and occurs in less than 1% of the general adult population. Binge eating is a common symptom associated with obesity, however. BED may be conceptualized as a psychiatric syndrome or it may be viewed as a behavioral symptom associated with obesity. We conclude that clarification of this conceptual issue is needed if research on BED is to progress.