Severe heart failure developed in a 49-year-old patient 18 months after orthotopic cardiac transplantation. Acute rejection as well as other overt causes of graft failure were excluded. Haemodynamic measurements suggested severe diastolic myocardial dysfunction. Since no other causes of diastolic heart failure were identified, a potential side effect from cyclosporine was considered. Cyclosporine was therefore withdrawn and immunosuppressive treatment was switched to conventional therapy consisting of azathioprine and prednisolone. Withdrawal of cyclosporine was followed by an impressive clinical improvement and by complete haemodynamic normalization. Therefore, in cases of otherwise unexplained graft failure, a potentially reversible side effect from cyclosporine should be taken into consideration.