The incidence of fungal infections in the Intensive Care Unit (ICU) has increased with the use of advanced medical and life support systems, the prolongation of the life and the increasing number of patients with severe underlying diseases altering the immune response (cancer, chemotherapy, transplantation, AIDS). Systemic fungal infections are associated with high morbitity and mortality rates. The diagnosis remains difficult in the absence of specific techniques able to distinguish colonization from invasive and disseminated disease. Treatment of fungal infections has been classified as prophylactic, early presumptive, empiric and definitive. Several antifungal agents are or will be available, including amphotericin B with or without liposomal formulations, azoles, flucytosine, nystatin, voriconazole, echinocardins and itroconazole. Immunomodulation therapy is under investigation. Some fungal strains have intrinsic or acquired resistance against antifungal drugs. The antifungal treatment can be associated with severe complications which can prolong the ICU stay of the patients and increase the cost of hospitalization. The prognosis of the systemic fungal infections is poor. Pneumon 2002, 15(1):14-30.