The purpose of this phase 2 study is to test the efficacy of azacytidine given prior to fludarabine, cytarabine, and G-CSF for the treatment of relapsed or refractory acute myeloid leukemia.

Inclusion Criteria:

1. Age 16 to 60

2. Patients with a diagnosis of relapse or refractory AML (≥ 20% blast in bone marrow).

3. Eastern Cooperative Oncology Group (ECOG) performance status ≤2

4. Patients must have preserved organ function as defined below:

   • Creatinine ≤ 1.5 mg/dl
   • Total bilirubin ≤ 1.5x upper limit of the normal
   • Alanine aminotransferase (ALT) ≤ 2x upper limit of the normal
   • Left ventricular ejection fraction (LVEF) ≥ 45%

Exclusion Criteria:

1. Patients with a diagnosis of acute promyelocytic leukemia (AML -M3)
2. Pregnant women
3. Patients previously treated with fludarabine are allowed to participate.
4. Patients with Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements.