We performed 56 HDIVG administrations in adults (26) and children (30) affected by idiopathic thrombocytopenic purpura with two different schedules: a five-day course at 400 mg/kg/d and a "bolus" 1 gr/kg. Forty-five cases were treated in preparation for surgical operations and eleven for bleeding episodes. Response to the five-day course in adults was good in 3/24, fair in 13/24, poor in 8/24, while in children it was good in 14/26, fair in 9/26, poor in 3/26. The difference between adults and children is statistically significant. None of the responder patients submitted to surgical operation needed platelet infusions during surgery. Response to the "bolus" schedule (6 cases) in adults was poor in 1 case and good in the other one, and in children, fair in 3 cases and good in the other one. In responder patients treated for bleeding episodes we obtained clinical improvement with hemorrhage arrest. In adults the treatment was well-tolerated, while in children we observed 3/30 mild side effects and 1/30 important side effect.