Antifungal chemotherapy in weakened resistance is restricted to the following three substances: amphotericin B, 5-fluorocytosine and the azo dyes. The paper only discusses the therapy of indigenous iatrogenic fungal infections due to mycelial fungi (molds) and yeasts. The pathogenesis must be investigated in every case, since a healthy individual does not contract such a fungal infection. Prophylaxis would be more important than treatment of such complications. At the end of the paper, the therapy is summarized in a table. It is clearly seen from the table that the optimal modern therapy of systemic mycoses is a combination of 5-fluorocytosine in a normal dosage and amphotericin B at reduced dosage.