Turner syndrome (TS) occurs in about 1:4000 live births and describes females with a broad constellation of problems associated with loss of an entire sex chromosome or a portion of the X chromosome containing the tip of its short arm. TS is associated with an astounding array of potential abnormalities, most of them thought to be caused by haploinsufficiency of genes that are normally expressed by both X chromosomes. A health care checklist is provided that suggests screening tests at specific ages and intervals for problems such as strabismus, hearing loss, and autoimmune thyroid disease. Four areas of major concern in TS are discussed: growth failure, cardiovascular disease, gonadal failure, and learning disabilities. GH therapy should generally begin as soon as growth failure occurs, allowing for rapid normalization of height. Cardiac imaging, preferably magnetic resonance imaging, should be performed at diagnosis and repeated at 5- to 10-yr intervals to assess for congenital heart abnormalities and the emergence of aortic dilatation, a precursor to aortic dissection. Hypertension should be aggressively treated. For those with gonadal dysgenesis, hormonal replacement therapy should begin at a normal pubertal age and be continued until the age of 50 yr. Transdermal estradiol provides the most physiological replacement. Finally, nonverbal learning disabilities marked by deficits in visual-spatial-organizational skills, complex psychomotor skills, and social skills are common in TS. Neuropsychological testing should be routine and families given support in obtaining appropriate therapy, including special accommodations at school.