Background. Intensity of exercise and low energy consumption, specific type and amount of training, early age at initiation, previous menstrual dysfunctions, low body mass index (BMI) or percentage body fat, pathological feeding habits and psychological stress have been suggested as potential factors accountable for menstrual irregularities in female athletes.Aim. To evaluate the influence of intensive training and of dietetic and anthropometric factors on menstrual cycles in female ballet dancers.Method. A case-control study, in which a structured interview and physical examination were carried out in two groups of teenagers aged between 12 and 18 years. The study included a total of 115 adolescent girls distributed in two groups: dancers (group B, n = 38) and girls of the same age not engaged in any sports activity (group C, n = 77).Results. Early starting high-intensity training delayed the onset of menarche ( p < 0.001). Dancers had a higher prevalence of oligomenorrhea and amenorrhea than control girls ( p = 0.004). Additionally, the dancers had lower scores in anthropometric variables: breast circumference 80 cm vs. 86.6 cm for controls ( p = 0.0001), low weight in 18% of dancers vs. 2.6% of controls ( p = 0.0001), and low height in 18% of dancers vs. 9% of controls ( p = 0.016). In addition, in dancers, low BMI was observed in 21% compared with 13% of controls ( p = 0.0001). Finally, 32% of the dancers were on a weight-control diet while this percentage decreased to 12% for the girls in control group (odds ratio = 3.49, 95% confidence interval = 1.31-9.25).Conclusions. In ballet dancers, high-intensity training was associated with late onset of menarche, menstrual disorders, lower weight and height development, and abnormal feeding behaviors.