The authors report their experience with eight patients (11 hips) with Down syndrome who sustained a slipped capital femoral epiphysis (SCFE). Six patients were diagnosed with hypothyroidism. All patients were greater than the 85th percentile for body mass index. Initial treatment was by in situ pinning in all hips. Six of the 11 slips progressed, 2 had collapse consistent with avascular necrosis, and 1 developed collapse secondary to joint sepsis and osteomyelitis. Additional surgery was necessary on seven hips. Four of eight hips followed until maturity had substantial femoral head deformity. Three of these patients had a noticeable limp and pain. Treatment of SCFE in patients with Down syndrome is difficult and the prognosis is guarded. These patients should be screened for hypothyroidism.