Nitric oxide (NO) is present in exhaled air in humans and its level may decrease in heart diseases. In the present study we prospectively investigated how heart transplantation treated with oral immunosuppresive drugs based on ciclosporine A influences the exhaled NO concentration (exNO). The study was performed in 17 patients after heart transplantation in various time after procedure and 15 nonsmoking healthy volunteers as a control group. Patients after heart transplantation were free of clinical signs of rejection. End-tidal concentration of exNO was measured by the use of a chemiluminescence method. We found no statistically significant differences in the exNO level between patients after heart transplantation and healthy controls (6.81+/-2.70 part per billion (ppb) in the transplant group vs. 6.01+/-3.43 ppb in the control group). We conclude that heart transplantation and immunosuppresive therapy do not influence the exhaled NO concentration.