Candida lusitaniae, a Candida species frequently resistant to amphotericin B (AMB), is a rare cause of candidemia. The clinical significance of this in vitro resistant phenotype, the risk factors for, and the clinical presentation of C. lusitaniae fungemia in comparison with those of Candida albicans have not been completely characterized. We reviewed 13 consecutive cases of C. lusitaniae fungemia in cancer patients and compared them with 41 consecutive cases of C. albicans fungemia (1990-2004). The AMB mutational frequency and rate of fungicidal activity was compared between a bloodstream, AMB-susceptible C. lusitaniae isolate associated with clinical failure and reference C. albicans and Candida glabrata strains. In multivariate analysis, patients having C. lusitaniae fungemia were more likely to have neutropenia (p=0.001), stem cell transplantation (p=0.014) and to have received prior antifungals (p=0.04). Mutational frequencies at clinically-achievable AMB exposures were 8 x 10(5) for C. lusitaniae and <1 x 10(9) for C. albicans and C. glabrata reference strains. Compared to C. albicans and C. glabrata, AMB had much less fungicidal activity against C. lusitaniae in time-kill curve analysis. Clinically, C. lusitaniae fungemia was more frequently associated with stem cell transplant and neutropenia. C. lusitaniae, even originally susceptible to AMB, might be less amenable to AMB therapy.