We have treated six transfusion-dependent, steroid-unresponsive, Diamond-Blackfan anaemia (DBA) patients with the recombinant human growth factors granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3), administered sequentially with an interim rest period. GM-CSF was given at a dose of 500 micrograms/m2/d subcutaneously for 6 weeks. Three patients increased their absolute reticulocyte counts 1.5-35-fold (mean 20.8-fold) and into the normal range, but only one showed a reduction in transfusion requirements. Between 4 and 25 weeks after discontinuation of GM-CSF, these six patients were treated with recombinant human IL-3, at doses of 60 or 125 micrograms/m2/d subcutaneously for 4-6 weeks. Three increased their absolute reticulocyte counts from 2- to 28-fold (mean 10.6-fold) and two required fewer transfusions. One of these two patients has remained transfusion independent for over a year since completion of IL-3 therapy, and the second patient required infrequent transfusions for 9 months and then became transfusion independent for the subsequent 5 months. The sustained clinical remissions seen in two of the six patients after IL-3 therapy is very encouraging and further studies in a larger cohort of DBA patients with IL-3 alone or in combination with GM-CSF or other growth factors should be carried out.