Amenorrhea is currently a criterion in the Diagnostic and Statistical Manual of Mental Disorders (4th ed., Text rev. [DSM-IV-TR]) for the diagnosis of anorexia nervosa (AN). Recently, there has been increased interest in examining the utility of this criterion. This article reviews the historical rationale for inclusion of amenorrhea in the DSM criteria for AN, clinical evidence evaluating amenorrhea as a diagnostic criterion for AN, and the nursing practice implications of amenorrhea as a diagnostic criterion for AN. Data suggest there is limited support for amenorrhea as a diagnostic criterion for AN.