Modifying induction therapy in acute myeloid leukemia (AML) may improve the remission rate and reduce the risk of relapse, thereby improving survival. Escalation of the daunorubicin dose to 90 mg/m 2 has shown benefit for some patient subgroups when compared with a dose of 45 mg/m 2, and has been recommended as a standard of care. However, 60 mg/m 2 is widely used and has never been directly compared with 90 mg/m 2. As part of the UK National Cancer Research Institute (NCRI) AML17 trial, 1206 adults with untreated AML or high-risk myelodysplastic syndrome, mostly younger than 60 years of age, were randomized to a first-induction course of chemotherapy, which delivered either 90 mg/m 2 or 60 mg/m 2 on days 1, 3, and 5 combined with cytosine arabinoside. All patients then received a second course that included daunorubicin 50 mg/m 2 on days 1, 3, and 5. There was no overall difference in complete remission rate (73% vs 75%; odds ratio, 1.07 [0.83-1.39]; P = .6) or in any recognized subgroup. The 60-day mortality was increased in the 90 mg/m 2 arm (10% vs 5% (hazard ratio [HR] 1.98 [1.30-3.02]; P = .001), which resulted in no difference in overall 2-year survival (59% vs 60%; HR, 1.16 [0.95-1.43]; P = .15). In an exploratory subgroup analysis, there was no subgroup that showed significant benefit, although there was a significant interaction by FLT3 ITD mutation. This trial is registered at http://www.isrctn.com as #ISRCTN55675535.