Graves' disease, which is the main cause of hyperthyroidism in the pediatric age group, is very rare in pre-school children. We describe the cases of four girls, aged less than 6 years old, out of a total of 30 patients diagnosed with Graves' disease between 1985 and 2004. Investigations were motivated by tachycardia, chronic diarrhea, language development delay or thyroid nodules detected by cervical ultrasonography. In three of the four patients height and bone age were advanced. In all patients goiter was small or absent. None of the patients had ophthalmic disease. In all patients free T3 and T4 were elevated and thyroid-stimulating hormone was suppressed. Three patients were positive for thyroid-stimulating immunoglobulins (the method was not available for the oldest case). Two patients showed complete resolution after 5 years of treatment with carbimazole. The remaining two patients are still under treatment and no adverse effects have been documented.