Graft rejection remains a major factor limiting long-term survival despite continued advancement in the use of immunosuppression. Aggressive surveillance for the detection of acute rejection is therefore necessary. Repeated endomyocardial biopsy (EMB) (at least 11 times the first year after transplantation) remains the only reliable surveillance method available. EMB is expensive, invasive, inconvenient to the patient, and associated with a significant incidence of serious complications. Therefore, it would be very important for patient care if new no-risk methods would prove to be effective in surveillance of rejection.