The outcome of high-risk (HR) Acute Lymphoblastic Leukemia (ALL) patients enrolled in AIEOP-BFM ALL 2000 study (NCT00613457) in Italy is described. Overall, 1999 Philadelphia negative ALL patients entered the study. HR criteria were: minimal residual disease (MRD) levels ≥10(-3) at day 78 (HR-MRD), no complete remission (no-CR) at day 33, t(4;11) translocation, Prednisone Poor Response (PPR). Treatment (2 years) included protocol I, 3 polychemotherapy blocks, delayed intensification (protocol IIx2 or IIIx3), cranial radiotherapy, maintenance. 312 HR patients (15.6% of the total) had 5-year event-free survival (EFS) and overall survival (OS) of 58.9%(SE 2.8) and 68.9%(2.6). In hierarchical order, EFS was 45.9%(4.4) in 132 HR-MRD patients, 41.2%(11.9) in 17 patients no-CR at day 33, 36.4%(14.5) in 11 patients with t(4;11), 74.0%(3.6) in 152 HR patients only for PPR. No statistically significant difference was found for disease-free survival (DFS) in patients with very high risk features (HR-MRD, no-CR at day 33, t(4;11) translocation), given HSCT (n=66) or chemotherapy only (n=88), after adjusting for waiting time to hematopoietic stem cell transplantation (HSCT) (5.7 months). Patients at HR only for PPR have favorable outcome. High risk MRD is associated with poor outcome despite intensive treatment and/or HSCT and may qualify for innovative therapies. The study is registered at the US National Institutes of Health website http://clinicaltrials.gov as "Combination Chemotherapy Based on Risk of Relapse in Treating Young Patients With Acute Lymphoblastic Leukaemia" with the protocol identification number NCT00613457.