From Dec. 1976 through June 1986, 474 patients with acute leukemia were treated with central nervous system (CNS) irradiation for the purpose of preventing relapse of CNS leukemia. Of the whole series, whole cranial irradiation at a dosage of 24 Gy and 4-5 intrathecal instillations of methotrexate (MTX) were given in 149 patients, simple intrathecal instillation of MTX in 44 patients and high dose intravenous MTX in 5 patients; the CNS relapse rates were 4.0%, 20.5% and 40.0% respectively. It was proved by our experience that whole cranial irradiation plus intrathecal MTX is the best approach to prevention of CNS leukemia relapses. © 1989 Chinese Journal Of Cancer Research.