A prospective study of the treatment of fungal infections with low-dose AmBisome enrolled 36 of 52 patients with thoracic malignancies who developed pulmonary fungal infections in the National Cancer Centre, Milan, over a 3.5 year period. Thirty-three high-risk patients had received standard prophylaxis with iv fluconazole. In these patients, symptoms indicating deep mycosis were detected after 7-9 days of primary prophylactic therapy. Another three patients, not treated with fluconazole, showed similar symptoms. Bronchoalveolar lavage, blood culture and/or CT scan of chest diagnosed invasive aspergillosis in 29 patients and deep invasive Candida infection in seven. AmBisome was given at 1-2.2 mg/kg/day i.v. for 10 days to avoid or decrease toxicity normally induced by amphotericin B. The fungal infection was eradicated in all 36 patients. Negative cultures were obtained after 5 or 6 days of antifungal treatment. No adverse reactions attributed to AmBisome were detected. After a follow up of 5-48 months, 30 patients were still alive. Six patients had died, two due to adult respiratory distress syndrome and four due to progression of cancer. No mycotic relapses or reinfections were detected during follow up. In a subset of critically ill patients with thoracic malignancies, the administration of low-dose liposomal amphotericin B (AmBisome) resulted in complete eradication of pulmonary Aspergillus and Candida infections, and was remarkably well tolerated.