In this preliminary study the efficacy of high-dose methylprednisolone (HDMP) during remission-induction chemotherapy was evaluated on 166 children with acute lymphoblastic leukemia (ALL). The St. Jude Total Therapy Study XI protocol with minor modifications was used in this trial. Patients were randomized into two groups. Group A received conventional-dose (2 mg/kg/day orally) prednisolone, and group B received high-dose methylprednisolone (HDMP, Prednol-L, 900-600 mg/m2 orally) during remission-induction chemotherapy. Complete remission was achieved in 97% of the children. For the 80 patients who were followed up for 3 years, median follow-up was 44 (range 5-60) months and the 3-year event-free survival (EFS) rate was 68.5%) overall, 58.6% in group A and 78.4% in group B. The EFS among patients in group B was significantly higher than in group A (p=0.05). When we compared the 3-year EFS of groups A and B in the high-risk groups and high-risk subgroups with white blood cell (WBC) counts > or = 50 x 10(9)/l and age > or = 10 years, the survival rates were 45% versus 77.2%, 33% versus 78% and 45% versus 89%, respectively. During the follow-up of 162 patients, relapses were significantly higher in group A. Bone marrow relapses in 162 patients, and also in a subgroup of patients > or = 10 years of age were significantly higher in group A. These results suggest that HDMP during remission-induction chemotherapy improves long-term EFS, particularly for high-risk patients.