This trial tested the safety and efficacy of a regimen consisting of hydroxyurea followed by azacitidine, 75 mg/m2 for 7 days, and gemtuzumab ozogamicin, 3 mg/m2 on day 8, in older patients with newly diagnosed acute myeloid leukemia. Those achieving a complete remission received 1 consolidation treatment followed by 4 cycles of azacitidine. The patients were stratified into good-risk (age 60-69 years or performance status 0-1) and poor-risk (age ≥70 years and performance status 2 or 3) groups. Specific efficacy and safety goals were defined as being supportive of further study of the regimen. Eightythree patients were registered in the good-risk cohort and 59 in poor-risk cohort, with median age of 71 and 75 years, respectively. In the good-risk group, 35 patients (44%) achieved a complete remission. Median relapse-free and overall survivals were 8 and 11 months, respectively. Six patients (8%) died within 30 days of registration. In the poor-risk group, 19 (35%) achieved a complete remission. Median relapse-free and overall survivals were 7 and 11 months, respectively. Seven patients (14%) died early. The results of this trial met predefined goals for efficacy and safety for the poor-risk cohort but not the good-risk group. This trial was registered at www.clinicaltrials.gov as #NCT00658814. © 2013 by The American Society of Hematology.