Following heart transplantation (HTx), patients often suffer from mycoses due to the necessary immunosuppressive treatment to prevent rejection episodes. Oropharyngeal Candida infections which mostly occur after HTx under high-dose immunosuppressive therapy can be avoided and treated successfully by prophylactic medication to be started immediately after transplantation, either by using azoles (e.g. fluconazole) or amphotericin B suspension. Contrary to this, invasive aspergillosis, beginning in the upper respiratory tract and the lung and mostly followed by hematogenous dissemination into various organs, is always a serious disease with high mortality. To avoid this infection, specimens from the respiratory tract, serum and urine should be examined mycologically prior to HTx. After HTx, apart from prophylactic avoidance of exposure to airborne fungal spores, close mycological control is mandatory to detect colonizations by aspergilli early. Timely administration of amphotericin B and 5-flucytosine, i.e. as soon as invasive growth is suspected, enables curative treatment of the often lethal course of this disease, even under immunosuppressive therapy.