The diagnosis of acute rejection in heart allograft recipients receiving cyclosporine is still an important challenge. The poor diagnostic value of clinical signs and the ECG means that regular endomyocardial biopsies must be performed. Despite their diagnostic value during the first year after transplantation, endomyocardial biopsies are less sensitive there after and currently suffer from the lack of a universally accepted histological classification. Doppler echocardiography can be used for routine surveillance and has proven reliable for the diagnosis of acute rejection with various clinical presentations when used in conjunction with endomyocardial biopsies. Immunohistological examination of myocardial specimens can further increase the sensitivity of histological diagnosis. Similarly, immunoscintigraphy with indium 111-labelled antimyosin antibodies is of value for the prediction of acute rejection after the first year. Therapeutic approaches have been standardized, but must still be tailored to the individual patient according to the severity of the rejection and the presence of associated infection and/or metabolic disturbances.