Four renal transplant recipients, treated with the immunosuppressive combination of azathioprine-prednisolone, developed organ or systemic mycoses caused by Candida albicans and, in one case, additionally by Trichophyton rubrum. Ketoconazole, a new wide-spectrum antimycotic drug, was successfully used in the treatment of the fungal infections in these patients. The oral route of administration, good tolerance and excellent results are good recommendations for this drug.