Results from the Children's Oncology Group have revealed that adding the monoclonal antibody gemtuzumab to standard chemotherapy improves event-free survival in children with acute myeloid leukaemia (AML) without excessive toxicity. The AAML0531 phase III trial randomly assigned 1,022 children (average age 10 years) to receive gemtuzumab or a standard treatment regimen, followed by additional chemotherapy for low-risk patients and stem-cell transplantation for high-risk patients. The addition of gemtuzumab did not improve overall survival significantly (74% versus 70%), but was associated with better disease-free survival (61% versus 55%) and reduced relapse risk (33% versus 41%).