We describe the outcome of children with B-precursor acute lymphoblastic leukemia registered on Pediatric Oncology Group 8602 who switched to Erwinia asparaginase (ASP) due to an allergy to the Escherichia coli product. Between February 1986 and January 1991, children in complete remission after induction that included intramuscular E. coli ASP (6000 U/m2×6) were randomized for consolidation. One regimen included intensive weekly intramuscular E. coli ASP (25,000 U/m2/wk×24). In case of an allergic reaction to E. coli ASP, Erwinia ASP was substituted at the same dose and schedule. Of the 540 eligible patients, 408 switched to Erwinia ASP due to an allergic reaction. Allergic reactions were significantly associated with younger age, white race, and standard-risk acute lymphoblastic leukemia. Multivariate Cox analysis adjusting for these factors demonstrated no correlation between the switch per se or the timing of the switch and event-free survival.