In an attempt to reestablish normal hematopoiesis in symptomatic myelodysplasia (MDS) and to show the tolerability of a combination treatment of low-dose cytosine arabinoside (LD AraC) and interleukin-3 (IL-3), we treated 31 patients (pts., median age 65 years) who had more than 10% blasts in the bone marrow (BM) and hematopoietic failure with LD AraC (2<10 mg/m2sc, day 1–14) plus IL-3 (once daily sc, day 8–21) at different dose steps (1.0, 2.5, 5.0, and 10.0μg/kg body weight). The numbers of' each 21-day cycle varied between 1 (3 pts.), 2 (6 pts.), 3 (8 pts.), 4 (1 pt.), 5 (5 pts.), and 6 (8 pts.), in total 116 cycles on an outpatient basis. Subjective tolerability was good in 20 cases (65%). Toxicities were fever (29 pts.), flu-like symptoms (17pts.), infections (15 pts.), hepatic toxicity (10 pts.), and skin reactions (8 pts.). Overall response was seen in 13 cases (42%) with 5 complete responses (CR), while 10 pts. had stable disease (SD), 5 progressed (2 to acute leukemia), 2 were considered toxic deaths, and 1 died due to the disease. Median survival is 18 months, progression-free survival is 12.5 months (18.0 months in responding pts.), with an actuarial follow-up of 31 months. The data from this phase I/II study show that a combination of LD-AraC and IL-3 is well tolerated and that stable responses can be achieved in MDS by means of an easy outpatient therapy.