Chronic idiopathic thrombocytopenic purpura (ITP) is an autoimmune disease characterized by the antibody-mediated destruction of platelets. To maintain the platelets above the symptomatic level we administered 100 micrograms of anti-D for 5 consecutive days to 19 children with ITP. Four patients did not respond to the treatment. Fifteen responded with an increase in the average platelet number to 76,000/microL 7 days postinjection. However, the platelet count dropped within 45 days to 27,000/microL. Three months after this study, two patients from the study group were then administered monthly anti-D after reinjecting anti-D daily for 5 consecutive days, as previously performed. Platelet levels in these two patients were maintained above 30,000/microL for 5 and 6 months respectively. We concluded that anti-D administration for 5 consecutive days can induce an increase in platelets followed by a decrease below 30,000/microL after 30-45 days. However, monthly administration of anti-D after daily injections for 5 consecutive days can keep platelets above the symptomatic level and may provide a corticosteroid-free safe interval for nearly 5 months.