Fungal infections are a common complication in hematological and oncological patients. In the study the results of a retrospective analysis of the onset of fungal infections among 383 patients admitted at the hematology unit of San Camillo Hospital, Rome, from 1980 to 1995 are reported. In the eleven years prior to 1991 only four cases of fungal infection were detected in high risk patients (1.8% of the high risk patients). From 1991 to 1993 there was a dramatic increase of fungal infections (Candida and Aspergillus). Thirteen cases of infections were observed during this period, eight of which were due to Aspergillus (12% of the high risk patients). For this reason it was decided to introduce a different prophylactic treatment for all high risk patients consisting of combined conventional intravenous (i.v.) amphotericin B, oral amphotericin B and nebulized amphotericin B, starting from the first day of hospitalization. Since the introduction of this new prophylactic regimen no cases of invasive fungal infections were observed in the 48 high risk patients examined. The prophylactic treatment was well tolerated by all patients. The results suggest that the combined use of oral, nebulized and i.v. amphotericin B is very effective in preventing invasive fungal infections in high risk patients.