Patients with myelodysplastic syndromes (MDS) who were anemic and/or thrombocytopenic were treated with 5-azacytidine (5-AZA) at a dose of 75 mg/m(2) per day SQ x 7 days. This cycle was repeated every 28 days. Forty-eight patients who received at least one cycle of 5-AZA were evaluable for response. Hematological toxicity was mild and consisted of thrombocytopenia and leukopenia. Extramedullary toxicity was uncommon and consisted of pneumonia, arthralgia, diarrhea, and injection site irritation. Eighteen of the 46 transfusion dependent patients became transfusion independent (39%). Median duration of response was 7 months with three patients continuing beyond 2 years. French Anglo British (FAB) classification and the International Scoring System (ISS) did not predict response to 5-AZA. However, a decrease in the white blood cells (WBC) during the initial cycle of 5-AZA correlated with a higher response rate.