Invasive fungal infections are associated with a high mortality and have been increasing in incidence over the last few decades. Candidemia and, less commonly, invasive pulmonary aspergillosis are the most relevant fungal infections in critical care medicine. Risk factors for systemic Candida infections are the use of broad-spectrum antibiotics, a prolonged stay in an intensive care unit and gastrointestinal injury or surgery. Invasive aspergillosis usually occurs in immunocompromised patients. The diagnosis of invasive fungal infections remains challenging. The therapeutic spectrum includes fluconazol, conventional and liposomal amphotericin B, and the recently introduced agents caspofungin and voriconazol. For rational and cost-effective use, the clinician requires precise knowledge of the indications and limitations of these agents. This review focuses on the diagnostic and therapeutic options in severe Candida infections and invasive aspergillosis.