Despite substantial progress in the treatment of AML, a proportion of patients do not achieve first complete remission (1^st CR) with the induction chemotherapy, and, among patients achieving it, a majority is expected to relapse within three years. As allogeneic hematopoietic stem cell transplantation has been established as the most effective form of antileukemic therapy in patients with AML in remission, many studies have focused on the reconstitution and the functionality of the innate immune system in this context, especially regarding cytotoxic effectors such as natural killer (NK) cells. On the contrary, very few data are available concerning the innate immune system of patients in 1st CR. Herein we investigated the phenotype of autologous NK cells of AML patients in 1st CR. We showed that immature NK cells were pre‐eminent in the blood of these patients and that this immature phenotype was persistent during the first months after 1st CR. Am. J. Hematol., 2010. © 2010 Wiley‐Liss, Inc.