The approved 7-day schedule of subcutaneous azacitidine for myelodysplastic syndrome is associated with injection site reactions and bruising and may be inconvenient because of the need for weekend doses. Although pharmacokinetic data with IV azacitidine suggests equivalence, there are no efficacy data published. Patients with all myelodysplastic syndromes (MDS) FAB subtypes were enrolled and received 75 mg/m(2)/d of azacitidine by 20-min intravenous infusion for 5 days in every 28 days. Global methylation studies were performed at baseline and prior to Cycle 3. Twenty-five patients were enrolled and 22 were evaluable. Median age was 69.5 years; 9 (41%) patients had lower-risk disease (IPSS Low or Int-1) and 13 (59%) had higher-risk disease (IPSS Int-2 or High). Twenty-seven percent of patients responded (5 CRs and 1 PR). The median time to response was 108 days. The median PFS was 339 days (11.3 months), the median OS was 444 days (14.8 months) and the median duration of response (DOR) was 450 days (15.0 months). Global methylation studies suggest a greater degree of demethylation in responders. This regimen appeared to offer a PR + CR rate and median DOR somewhat similar to what has been reported with the 7-day subcutaneous regimen; however, OS was shorter.