OBJECTIVE: Immunsuppressive therapy is a major therapy for severe aplastic anemia, and antithymocyte /antilymphocyte globulin (ATG/ALG) is usually used. This study investigated the therapeutic effect of ATG/ALG on severe aplastic anemia and explored the management of therapy-related complications. METHODS: Clinical data of 28 children with severe aplastic anemia who received ATG/ALG treatment from December, 1994 through to September, 2005 were analyzed retrospectively. RESULTS: Of the 28 patients, 2 were nearly cured (7.1%), 4 were relieved (14.3%) and 12 were improved (42.9%) based on a hemoglobin/white blood cell/platelet count. These results represented an overall effective rate of 64.3%. Clinical evidence of serum sickness developed in 19 patients, manifesting as fever (n=9), cutaneous eruptions (n=12), arthralgias (n=7), myalgia (n=7) and arthrocele (n=3). Serum sickness occurred 5-17 days after ATG/ALG administration and lasted for 1-15 days (mean 4.4 days). Three children with mild serum sickness symptoms recovered without any treatment. The symptoms of the other 16 patients disappeared after 3-5 days of methylprednisolone treatment (10 mg/kg daily). However, 3 patients had relapses at 2-4 days after termination of methylprednisolone therapy. Another course of methylprednisolone therapy was administered to the 3 patients until the symptoms disappeared. The patients with no serum sickness or with mild serum sickness had a better response to ATG/ALG therapy than those who had severe serum sickness (100% vs 60%; P<0.05). CONCLUSIONS: ATG/ALG therapy for severe aplastic anemia is effective. Serum sickness is a common complication in children with severe aplastic anemia following ATG/ALG therapy, but can be improved by methylprednisolone application.