Background/Aim: To investigate weight and growth requirements for menarche in girls with eating disorders (ED), weight loss and primary amenorrhea. Methods: Growth charts from school health services and measurements of weight and stature throughout treatment were obtained for 47 such girls. Results: Weight loss started at an age of 12.4 ± 1.6 years from a top weight of 41.7 ± 7.1 kg. Approximately a year later they had lost 5.1 ± 4.3 kg and grown only 2.8 ± 3.5 cm. Following treatment and weight gain, growth accelerated and the girls reached a peak growth velocity of 4.3 ± 2.6 cm/year 2 years before menarche which occurred at an age of 15.5 ± 1.6 years at a weight of 52.2 ± 5.3 kg. Menarche occurred within a wide range of weights but could be predicted by a linear regression on prepubertal weight (R<sup>2</sup> = 0.39; p < 0.001). Conclusions: Following treatment, girls with ED and primary amenorrhea progress through puberty at a slowed rate. The weight required for menarche can be predicted by the prepubertal weight which may represent the individual’s normal growth track unaffected by the ED.