Amenorrhea in the athlete is commonly encountered in clinical practice. The work-up of an athlete with amenorrhea should include consideration of all the physiological and pathological conditions that give rise to amenorrhea in any adolescent. Delay or failure to recognize and manage these patients may result in the emergence of athletic triad with potential serious consequences of increased stress fractures, scoliosis, and thin body mass. This article reviews amenorrhea in the adolescent athlete with respect to body composition, disordered eating, osteoporosis, psychological factors, warning signs, treatment, and outcomes. Need for further strategies specific to prevention, surveillance, research, health consequences, medical care, and public and professional education is addressed.