Azacitidine and decitabine are the two hypomethylating agents approved by the Food and Drug Administration for the treatment of patients with myelodysplastic syndrome (MDS). The efficacy of one agent post-failure of the other is unknown. Fourteen patients with MDS post-azacitidine failure/lack of response/intolerance were treated with decitabine. Overall three patients achieved a complete remission, and one patient had hematologic improvement, for an overall response rate of 28%. Of the responders, one stopped prior 5-azacitidine owing to disease progression, two for no response and one for severe skin toxicity. Grade 3-4 drug related side-effects were minimal. Global methylation studies in patient samples showed decrease of methylation after treatment with decitabine. As in our previous studies, there was no difference in hypomethylation between responders and nonresponders. We conclude that clinically significant responses with decitabine can be seen in patients post-azacitidine failure without significant toxicity.