BACKGROUND: An 8.5-year-old boy was referred to a pediatric endocrinology clinic for evaluation of short stature. At birth, a chordee without hypospadius, 90-degree penile torsion and an undescended testis on the right had been observed. The boy had undergone surgical repair at 1 year of age and at that time an undescended 'nonfunctional' streak gonad and a horseshoe kidney had been noted. Subsequent karyotype analysis had revealed a 45,X0/46,XY karyotype with mosaicism. Since 4-5 years of age, the patient's height has been below the 3(rd) percentile, whereas his weight has been maintained at approximately the 3(rd) percentile. INVESTIGATIONS: Performance of thyroid function tests, measurement of levels of insulin-like growth factor I and insulin-like growth factor binding protein 3, estimation of bone age, calculation of height and weight percentiles and SD scores based on 2000 normative data from the National Center for Health Statistics, USA. DIAGNOSIS: Mixed gonadal dysgenesis with a 45,X0/46,XY karyotype. MANAGEMENT: The patient's growth was found to be following the 50(th) percentile growth curve on the Turner syndrome growth chart, which was significantly below his mid-parental target height. He was started on growth hormone at a dose of 0.35 mg/kg/week. The patient remains under close follow-up to monitor his linear growth velocity and his pubertal development.