1. Previously untreated AML (>/= 20% blasts) or AML M6. Patients with high-risk (intermediate-2 or high by IPSS or >/= 10% blasts) MDS will also be eligible. Prior therapy with hydroxyurea, biological or targeted therapy (e.g. flt3 inhibitors, other kinase inhibitors, azacitidine), or hematopoietic growth factors is allowed. No prior chemotherapy is allowed except for a single or a two day dose of cytarabine (up to 3 g/m2) for emergency use is also allowed as prior therapy.