This chapter presents a state of the art summary of acute myeloid leukemia (AML) to its definition, biology, epidemiology, disease mechanisms, clinical signs, diagnosis, treatment and prognosis. AML is the most common malignant myeloid neoplasms and results from a clonal proliferation of progenitor myeloid cells that concurrently lose their normal ability to differentiate into mature myeloid cells. Cytogenetic abnormalities form the basis for the three main prognostic categories in AML, with the largest cytogenetic group being that with normal cytogenetics, comprising about 45% of adult AML cases and with intermediate prognostic risk. AML occurs far more commonly in adults and in men compared with women, with 67 years as the median age at diagnosis. Complete remission of AML is defined as a marrow with fewer than 5% blasts, a neutrophil count greater than 1,000, and a platelet count greater than 100,000.