Purpose To eliminate the toxicities and sequelae of cranial irradiation (CrRT) and to minimize the adverse impact of traumatic lumbar puncture (TLP) with blasts, a prospective study of a modified CNS-directed therapy was conducted in children with acute lymphoblastic leukemia (ALL). Patients and Methods Since June 1999, children with newly diagnosed ALL have been treated with triple intrathecal therapy (TIT) alone without CrRT. The first TIT was delayed until the disappearance of blasts from peripheral blood (PB) for up to 10 days of multidrug induction, and CrRT was omitted in all patients. If PB blasts persisted on treatment day 10 (d10), the TIT was then performed. Results Of a total of 156 patients, 152 were eligible. Seventeen patients did not have PB blasts at diagnosis. Three fourths of the remaining patients achieved complete clearance of PB blasts by d10. Only hyperleukocytosis at diagnosis showed a significantly lower clearance rate. Six standard-risk patients were upgraded to high risk because of detectable PB blasts on d10. TLPs were encountered in four patients (2.6%), but none were contaminated with lymphoblasts. Neither CNS-2 (less than 5 WBCs/μL with blasts in a nontraumatic sample) nor CNS-3 (≥ 5 WBCs/μL with blasts in a nontraumatic sample or the presence of cranial nerve palsy) was present. The 5-year event-free survival and overall survival rates ± SE were 84.2% ± 3.0% and 90.6% ± 2.4%, respectively. No isolated CNS relapse occurred, but two patients experienced combined CNS relapses. The 7-year cumulative risk of any CNS relapse was 1.4% ± 1.0%. Conclusion Delaying first TIT until circulating blasts have cleared may improve CNS control in children with newly diagnosed ALL and preclude the need for CrRT.