Acute myeloid leukemia is an aggressive myeloid neoplasm characterized by ≥20% myeloblasts in the blood or bone marrow. Current treatment strategies for acute myeloid leukemia are based on both patient-related parameters such as age and performance status as well as the intrinsic characteristics of particular disease subtypes. Subtyping of acute myeloid leukemia requires an integration of information from the patient's clinical history (such as any prior preleukemic myeloid neoplasm or cytotoxic potentially leukemogenic therapy), the leukemia morphology, cytogenetic findings, and the mutation status of particular genes (NPM1, FLT3, and CEBPA). In recent years, a barrage of information has become available regarding gene mutations that occur in acute myeloid leukemia and their influence on prognosis. Future therapies for acute myeloid leukemia will increasingly rely on the genetic signatures of individual leukemias and will adjust therapy to the predicted disease aggressiveness as well as employ therapies targeted against particular deregulated genetic pathways. This article reviews current standards for diagnosing and classifying acute myeloid leukemia according to the 2008 WHO Classification. Data that have subsequently accumulated regarding newly characterized gene mutations are also presented. It is anticipated that future leukemia classifications will employ a combination of karyotypic features and the gene mutation pattern to stratify patients to increasingly tailored treatment plans.