Study Objective: To determine 1) menstrual weight (% normal body weight at which menses resumed or began following anorexia nervosa) and 2) effects of anorexia nervosa on subsequent fertility.Design: Retrospective, blinded interviews of patients.Setting: Outpatient.Participants: Cohort of 83 amenorrhec adolescent females hospitalized consecutively between January 1, 1979 and September 31, 1988 on an Adolescent Medicine unit for the treatment of anorexia nervosa, interviewed ≧4 years posthospitalization.Interventions: None.Main Outcome Measures: 1) Menstrual weight (reported weight on resumption or initiation of menses, expressed as % normal body weight for height), and 2) fertility history.Results: Menses was occurring in 83% of subjects at follow-up. The menstrual weight averaged 92.1 ± 7.4 (SD)%. The % body weight for menstruating vs. amenorrheic subjects was 99.2 ± 13.6 (SD)% vs. 86.6 ± 7.7%, respectively (p = 0.0001). All females who wanted to conceive were able to do so within 1 year of trying to become pregnant.Conclusions: Following anorexia nervosa, menses can be expected to resume when weight reaches 92% of normal weight for height. A history of anorexia nervosa is unlikely to affect fertility if weight is restored to normal.