One hundred and five consecutive primary high-risk myelodysplastic syndromes (MDS) or secondary acute myeloid leukaemia (sAML) evolving from MDS (performance status 0-3, ECOG) entered this study. Induction chemotherapy (CT) consisted of idarubicine 12 mg/m2 i.v. on days 1 and 2, etoposide 60 mg/m2/12h i.v. for 5d, Ara-C 120 mg/ m2/12h i.v. for 5d (one or two courses). Patients were randomized to receive or not G-CSF (5 microg/kg/d subcutaneously 48 h after the end of CT). 52 cases underwent CT alone and 53 CT+G-CSF. The CT+ G-CSF patients had a significantly shorter duration of neutropenia (8 nu 16d) with a lower incidence of infections and significantly better responses (CR+PR: 74% v 52%, P<0.05). 40 patients entered CR: 17 with CT and 2 3 with CT+G-CSF. Responders underwent two consolidation courses with the same CT, followed by high-dose Ara-C (2 g/m2 every 12h for 3 d). Most CRs were clonal. At present 21 responders have relapsed (median relapse-free survival 4 5 months). Eight responders received an allo-BMT, six are alive in CR 7-57 months post-transplant. Therefore allo-BMT only increases the chance of a long survival and possible cure. In conclusion, CT+G-CSF did not prolong either CR duration or survival; the growth factor support, however, increased the number of allo-transplantable cases by inducing higher remission rates and improving clinical conditions.