n intense preoccupation with leanness and low body weight exists in the athletic population. This is especially apparent in young female athletes. M'ith strong intrinsic and extrinsic pressure to perform and the need to appear lean and fit, training is often taken to extremes. Whether the athlete's goal is to improve performance, become "ultra fit," o r lose weight, the results are often similar in the female population: menstrual irregularity, namely amenorrhea. While the absence of menses may be a pleasant convenience for the female athlete, she may be completely unaware that her skeleton could suffer irreversible consequences, such as decreased peak bone mass and eventual osteoporosis (7,38). Athletic amenorrhea, also termed hypothalamic hypogonadism (23), has been shown to cause substantial decreases in bone mineral density (BMD) at various sites in the body, especially in areas of high trabecular content (10,13,14, 29,32,38,44). Unfortunately, the loss of BMD is a silent process, and the athlete is usually unaware that a problem exists until a related injury, such as a stress fracture, occurs.Numerous variables are thought to be associated with athletic amenorrhea: training intensity, hours spent training, diet, body weight, body composition, age of menarche, type of sport, and psychological stress (8, l2,29). While many authors have sought to determine the specific cause of menstrual irregularities in female athletes, n o evidence exists demonstrating that a single risk factor is responsible (32). Therefore, it is likely that all (or at least several) of these factors are working in concert and contribute to menstrual disturbance (7,12,32,40).Regardless of the cause, menstrual irregularities are common among female athletes ( 1 2-15,23). As many as 51 % of endurance runners (1 1 ), 44% of ballet dancers (5), and 12% of swimmers and cyclist3 (45) have reported menstrual disturbances during periods of training. Rutherford (44), who studied female triathletes, found that 50% of the subjects experienced menstrual disturbances. Furthermore, these women reported that "[menstrual irregularities] were representative of the general incidence among good triathletes." Although resumption of menses usually occurs following a reduction o r cessation of training (13,15,41), it is not known if the decrease in BMD is permanent and will predispose the women to stress fractures or osteope rosis (1 3,15,32,4O).In addition to the large number of variables involved in these studies, interpretation of the results is made difficult by the lack of standard definitions of menstrual categories. Criteria for amenorrhea have ranged from