The aim of this study was to investigate thiotepa (TT) and fludarabine (Fluda) as a preparative regimen for allogeneic peripheral stem cell transplant in patients not eligible for a standard myeloablative regimen due to comorbidities and/or poor performance status. TT was given at a dose of 10 mg/kg over 2 days and Fluda at 125 mg/m2 over 5 days. In all, 21 patients (14 male, seven female; 10 acute leukaemia, eight myelodysplastic syndrome, two non-Hodgkin's lymphoma, one Hodgkin's disease) were treated. The median age was 51 years (range 30–55 years). All patients achieved full donor-type chimaerism. Adverse events included mild nausea and vomiting in two patients and a slight increase of serum amylase in three. A total of 13 patients received RBC transfusions (median 6 U, range 1–23), and all received platelets (median 4 U, range 1–27). Four patients died of nonrelapse causes and five of relapse. The 1-year probabilities of transplant-related mortality and relapse were 19 and 29%, respectively. In total, 12 patients remain in complete remission (median follow-up: 786 days). The 3-year overall survival probability was 58%. We conclude that this regimen is feasible and well tolerated.