We report on a patient with very severe aplastic anemia (SAA) unresponsive to immunosuppressive therapy (cyclosporine A, ATG). Because no HLA-identical family or unrelated donor could be found, a trial with recombinant human granulocyte stimulating factor (G-CSF) was started. This was followed by a rapid 3-lineage response with near-normal blood counts and transfusion independence. A similar response was obtained by 2 further G-CSF cycles which were given for relapsing SAA after G-CSF withdrawal. Following the third cycle, an acquired platelet function disorder was observed which preceded a myelodysplastic syndrome.