Graft-versus-tumour reactions as a form of adoptive immunotherapy may help prevent the recurrence of haematological malignancy following allogeneic BMT. We hypothesised that such reactions may be maximised by shortening the duration of post-transplant immunosuppression by a rapid taper of cyclosporine (CYA). CYA dose was tapered between days 30 and 60 in patients at high risk of relapse, provided there was no evidence of prior significant acute GVHD. Twenty-six of 58 high-risk patients eligible at the time of transplant were subsequently tapered. Seven (27%) developed grade III/IV acute GVHD after completion of the taper, which was fatal in one patient. Chronic GVHD was observed in most patients, although with minimal overall impact on performance status. The overall probability of survival at 2 years was 43%. This non-randomised experience indicates that a rapid taper of CYA is tolerable and may provide an alternative to immunotherapy with donor leukocyte infusion in the high-risk allograft setting.