Eight patients with myelodysplastic syndrome (MDS; RA = 1, RAEB = 2, RAEB-t = 4, CMML = 1) received three cycles of recombinant gamma-IFN administered in 2-week intervals, each consisting of a 14-day period of subcutaneous injections at a daily dose of 0.1 mg/m2. Neither a complete nor a partial remission could be obtained. There was only one definite improvement consisting in a rise of hemoglobin level from 7 to more than 12 g/dl. Two minor improvements were due to a slight rise of platelet counts. Three patients developed acute leukemia under treatment with gamma-IFN. Our data suggest that gamma-IFN administered according to the treatment schedule as used in our trial has only a minimal beneficial effect in patients with MDS.