The outcome of a cohort of 218 consecutive patients who failed to respond to a single course of standard daunorubicin plus ARAC (three + seven) induction regimen has been retrospectively evaluated to assess the characteristics of this group of AML patients and the effectiveness of second-line induction programs. Seventy-four of the 218 patients (33.9%) attained complete remission with salvage chemotherapies. The multivariate analysis of pretherapy characteristics of the patients showed that peroxidase positivity and age were the most important factors in determining whether or not the patient would have a favorable response to second-line induction regimen. In addition, comparison of marrow characteristics at diagnosis with those of marrow after the first-line therapy (marrow leukemic index, MLI) provided the greatest differences between second-line CR and resistant patients. Finally, peroxidase positivity and MLI predicted for remission duration and overall survival. Allogeneic BMT, however, appeared the most important factor for survival and event-free survival of remitting patients. These results are of importance when considering that better defined prognostic factors provide an objective rationale for selecting appropriate strategies for the treatment of patients who do not respond to a single course of induction regimen.