PURPOSE: Acute leukemia with hyperleukocytosis (more than 105/mm3) is at high risk of early sudden death, usually from intracerebral hemorrhage. Emergency cranial irradiation is a relatively simple approach to solve this the problem. We summarized our experience of cranial irradiation in 24 leukemic children who presented with hyperleukocytosis. METHODS AND MATERIALS: Between 1990 and 1998, 40 children with acute leukemia presenting with hyperleukocytosis were referred for emergency cranial irradiation. Among these patients, 24 children were evaluable. There were 16 boys and eight girls, their ages ranged from 2 to 13 years (median 9.5 years). The initial leukocyte counts ranged 109,910/mm3 to 501,000/mm3. Peripheral blood smear was performed in all patients and noted the morphology of the blast. Introduction of emergency cranial irradiation was determined by the leukocyte counts (more than 100,000/mm) and the existence of the blast in peripheral blood smear. All patients were treated with intravenous hydration with alkaline fluid and oral allopurinol. Cranial irradiation started on the day of diagnosis. With 2 Gy in one fraction in 4 patients, 4 Gy in two fractions in 20 patients. RESULTS: The WBC count had fallen in 19 patients (83%) and no intracerebral hemorrhage occurred after irradiation. There were five cases of early deaths. Four patients died of metabolic complications, and one patient with intracerebral hemorrhage. He died 5 hours after cranial irradiation. No patient had any immediate side effect from cranial irradiation. CONCLUSION: Our data suggest, that emergency cranial irradiation can be safely chosen and effective in childhood leukemic patients presenting with high leukocyte counts.