Fungi such as Fusarium spp., Curvularia spp., Alternaria spp. or Trichosporon beigelii, had been thought to represent contamination or harmless colonization when isolated from humans. More recently, the role of these and other newly recognized fungi as serious pathogens has been clearly established. Three diverse groups of fungi are responsible for these infections: the agents of phaeohyphomycosis and hyalohyphomycosis and certain yeasts. These infections, which have been encountered in both presumably healthy and immuno-compromised individuals, tend to be localized in the former, and disseminated and frequently fatal in the latter group of patients. A major concern is that these organisms are not uniformly susceptible to amphotericin B. Standardization of antifungal susceptibility testing may, therefore, be helpful in determining the antifungal drug of choice for each infection. It is also hoped that the advent of newer antifungals and biologic response modifiers will have a significant impact on the morbidity and mortality of these emerging infections.