 The activity of histone deacetylase HDAC inhibitor, Vorinostat or Suberoylanilide hydroxamic acid SAHA, against AML has been suggested in cell line models and in animal model as well as in a phase 1 trial. The phase 1 study determined the MTD of oral Vorinostat as 200mg twice daily or 250mg thrice daily. In addition, the phase 1 trial showed the antitumor activity of Vorinostat with 17 of response rate in patients with advanced leukemia or myelodysplastic syndrome MDS. Accordingly, further study is recommended to demonstrate the clinical activity of Vorinostat in AML. 