This is an open label Phase II study. Patients will receive Vidaza for 5 consecutive days (Days 1- 5) of each 28-day cycle. Complete androgen ablation will be continued. Response will be assessed after a minimum of 2 cycles (evaluable patients). PSA response will be evaluated prior to each cycle and % fetal hemoglobin will be evaluated prior to each odd cycle (excluding Cycle 1). Patients will be treated until clinical progression up to a maximum of 12 cycles. A total of 35 patients with advanced metastatic HRPC will be enrolled in this trial.