A cooperative Italian study group on acute idiopathic thrombocytopenic purpura (AITP) has been designed to evaluate efficacy and safety of no treatment at the onset of the disease and sequential treatment with immunoglobulin and high dose steroid. One hundred thirty-eight patients with AITP entered in the trial. Eleven patients were treated before the end of the waiting period because of bleeding. One hundred twenty-seven (92%) received no treatment for the first 10 days of the disease, 65 patients (51.18%) recovered spontaneously, 62 patients were treated with immunoglobulin, and 52 (83.8%) of them responded positively but only 36 (58.06%) permanently. There was no statistical difference between the results obtained with 400 mg/kg for 5 days versus 200 mg/kg. Twenty-four patients were treated with high doses of steroids, 20 (83.3%) with positive response, and 10 (41.66%) were permanently cured. Four (3.14%) of the patients enrolled in the protocol still had active disease at the end of treatment, and 10 relapsed within 4 months after the end of the treatment.