We report a high incidence of myelodysplastic syndrome (MDS)/acute myeloid leukaemia (AML) in patients entered into the Medical Research Council Chronic Lymphocytic Leukaemia-5 trial. Of 115 newly diagnosed patients treated with fludarabine, 65 patients proceeded to autologous transplant. Conditioning was cyclophosphamide and total body irradiation in 49 (75%) patients and chemotherapy in 12 (18%). Ten patients have developed MDS/AML; eight had undergone an autograft. Five-year actuarial risk of developing MDS/AML postautograft was 12.4% (95% confidence interval, 2.5-24%). No analysed potential risk factor was predictive for MDS/AML development. We hypothesise that potential causative factors are fludarabine, low cell dose and transplant conditioning
