We are studying the combination of decitabine, arsenic trioxide and ascorbic acid, two primary agents and one vitamin all with different mechanisms of action in order to improve the response rate in patients with MDS and AML. This is an open-label, single-arm, single-center, dose escalation Phase I trial of decitabine, arsenic trioxide and ascorbic acid in patients with MDS, either de novo or secondary, fitting any of the FAB classifications and AML.