Cytarabine (araC) has served as the backbone of acute myeloid leukemia (AML) treatment for nearly forty years. High-dose cytarabine (HD araC) therapy resulted from a theoretical model developed in the 1970s that attempted to maximize the anti-leukemia effect of cytarabine. Since that time, HD araC has been utilized mostly in consolidation therapy for AML and in patients with relapsed or resistant AML. The development of araC and HD araC preceded our current understanding of AML biology-that it is a heterogeneous disease, not a single clinical entity. Thus, the optimal dose, schedule, and clinical setting for the use of cytarabine in hematologic malignancies remain uncertain. Research is now better defining the optimal use of HD araC based on leukemia cell karyotype and molecular signature. Here we review the pharmacodynamics of araC, the landmark studies that established the role of HD araC in AML, and research defining the role of HD araC based on the unique biologic properties of the leukemia cell.