Oral candidiasis due to azole-resistant Candida albicans is an increasing problem in patients with AIDS who received prolonged periods of fluconazole prophylaxis. Infection with C. albicans is also frequent in patients undergoing transplantation. However, azole resistance has not been appreciated as a major problem for these patients, presumably because they receive a relatively short duration of fluconazole prophylaxis. We describe a case of disseminated candidiasis due to fluconazole-resistant C. albicans in a patient following marrow transplantation. Restriction fragment length polymorphism analysis with use of the C. albicans strain-specific Ca3 probe was performed on sequential isolates. Identical banding patterns were obtained, thereby confirming that a fluconazole-susceptible endogenous C. albicans acquired azole resistance during a brief exposure to the drug and subsequently caused disseminated infection. This observation raises questions regarding the incidence, significance, and mechanism of azole resistance in fungi causing infection in this population.