We report the use of alpha 2b-interferon in 15 children with symptomatic, chronic idiopathic thrombocytopenic purpura, who did not respond to standard therapy. The platelet count increased in nine children during therapy. In six children the increase lasted less than 6 weeks. An increased platelet count was seen when a higher dose was used in two of four initial nonresponders. One responder who relapsed had an identical response when retreated with the same dose. No significant side effects were documented. Further studies are required to establish the optimal dose and administration schedule of alpha 2b-interferon for use in children with chronic idiopathic thrombocytopenic purpura.