I. To determine the maximal tolerated dose (MTD) and dose limiting toxicities (DLT) of vorinostat in combination with Decitabine in patients with relapsed/refractory or poor prognosis acute myelogenous leukemia (AML), acute lymphocytic leukemia (ALL), myelodysplastic syndrome (MDS) or chronic myeloid leukemia in accelerated or blastic phase (CML-BP).