Standardized criteria for complete remission (CR) in acute myeloblastic leukemia (AML) require the absence of peripheral blood blasts (PBBs). However, MD Anderson (MDA) criteria for CR (CR-MDA), although including the other requirements for CR, have not included the PBB count. We exploit this difference to assess the effect of PBBs at the time of CR-MDA on relapse-free survival (RFS) time. Eighty percent of the 533 patients with newly diagnosed AML or refractory anemia with excess of blasts (RAEB) entering CR-MDA from 1995 to 2000 had no PBBs at time of CR-MDA. Ninety-three percent of the remaining patients, who thus had CR-MDA but not standard CR, had 1% to 5% PBBs at this time. Multivariate analyses, using both conventional and Bayesian approaches, indicated that PBBs had no effect on RFS. For all patients and for the subgroups given and not given granulocyte colony-stimulating factor (G-CSF), the 95% credible interval for the relative risk of failure in the PBB group was nearly centered at 1.0. Thus, our data do not support use of PBBs in defining CR in newly diagnosed AML.