 In terms of the combining drug with Vorinostat, anthracycline is one of the best candidate. A in vitro study demonstrated that the combination of anthracycline esp. idarubicin with HDAC inhibitor have significant clinical activity against leukemia. Another candidate is Gemtuzumab ozogamicin, which is a calicheamicin-conjugated antibody directed against CD33 antigen on AML blasts. The U.S. FDA also approved the use of GO in relapsed AML as a monotherapy. A study also showed that the combinational therapy of GO with attenuated doses of standard induction chemotherapy could successfully induce CR without increasing treatment-related mortality in AML patients aged 55 or older. A in vitro study reported that HDAC inhibitor valproic acid augmented the clinical activity of GO toward CD33 AML cells. The study demonstrated that the strategy using HDAC inhibitor together with GO could potentially induce synergistic proapoptotic activity against AML blasts without increasing toxicity. In our center, so far we treated relapsed or refractory AML patients using the salvage regimen including GO 3mgm2dayx1day plus attenuated IdarubicinCytarabine Idarubicin 12mgm2day for 2 days and intermediate dose Cytarabine. So far, the CR rate from the regimen is around 50 without increasing TRM. Accordingly, we will determine the efficacy and toxicity of Vorinostat-incorporating salvage regimen based on the GOIA chemotherapy in patients 50 years old or older with relapsed or refractory AML. 