Acute myeloid leukemia preceded by a myelodysplastic syndrome (MDS-AML) is generally regarded as a high-risk type of AML, where remissions are rare and of short duration. Recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) is suggested to increase the sensitivity of leukemic cells to cycle-specific drugs. In this study 14 MDS-AML patients were given rhGM-CSF together with standard induction chemotherapy (TAD). rhGM-CSF was started 48 h prior to chemotherapy and given for up to 3 weeks. The results showed eight (58%) complete and two (14%) partial remissions, while another two (14%) patients had minor responses. One patient relapsed after 1 year, and then responded a second time. rhGM-CSF had to be stopped owing to local allergic reactions in two patients, both non-responders, but was otherwise well tolerated. Compared with our historical group of controls we found significantly higher remission rates, fewer early deaths, fewer fever days, and fewer days with both neutropenia and thrombocytopenia among the patients treated with rhGM-CSF and TAD. The estimated median over-all survival was 332 days. The severity of initial myelodysplastic changes did not correlate to the outcome of therapy but the degree of peripheral blood dysplasia decreased among responding patients. MDS-AML patients in this pilot study did respond better, and with minimal toxicity, when standard induction chemotherapy was given in combination with rhGM-CSF.