Children with Philadelphia (Ph) chromosome positive (+) acute lymphoblastic leukemia (ALL) represent a subgroup at very high risk for treatment failure. This study included 1322 children enrolled between 1988 and 1994 on CCG risk-adjusted studies for ALL who had centrally reviewed cytogenetic data. Thirty patients had a t(9;22) and are referred to as Ph+; 1292 were Ph-. 23 of these 30 patients were treated on the CCG-1882 high risk ALL protocol. The event-free survival (EFS) outcome in CCG-1882 was significantly worse for Ph+ compared with Ph- patients, with 4-year estimates of 11.3% (SD = 9.8%) and 73.4% (SD = 2.3%), respectively (p < 0.0001).