The authors recruited 229 treatment-seeking anorexic and bulimic women for a prospective, longitudinal study. Telephone interviews were arranged every 3 months for at least 1 year for 225 patients. At intake, 132 subjects were menstruating, 34 subjects were taking oral contraceptives, 5 subjects had an organic cause for amenorrhea (e.g., hysterectomy), and 58 subjects were amenorrheic. Each patient met Diagnostic and Statistical Manual of Mental Disorders, third edition, revised (DSM-III-R) criteria for anorexia nervosa (AN, N = 41), bulimia nervosa (BN, N = 98), or AN/BN (N = 90). All subjects were interviewed with the Schedule for Affective Disorders and Schizophrenia-Lifetime Version, which was modified to include a section for DSM-III-R eating disorders, the Longitudinal Interval Follow-Up Evaluation, and the Structured Interview for DSM-III Personality Disorders. It was found that body weight was associated with menstrual status: those with amenorrhea had a mean percent ideal body weight (IBW, Metropolitan Life criteria) of 74 +/- 1% compared with 102 +/- 19% for menstruating patients (p < .01). Affective illness was more prevalent among patients with amenorrhea than among menstruating patients (75% vs. 56%, p < .05). Menses were regained within 1 year by 33% of amenorrheic patients. These patients gained an average of 7.3% of their IBW. Longer duration of eating disorder (p < .03) and the presence of an anxiety disorder (p < .05) were associated with persistent amenorrhea. Menses were lost within 1 year by 8% of menstruating patients. These patients lost an average of 5.0% of their IBW.(ABSTRACT TRUNCATED AT 250 WORDS)