In this study, we evaluated the value of the Platelia(®) Candida mannan antigen (Ag) sandwich enzyme-linked immunosorbent assay test in the diagnosis of invasive candidiasis (IC) and the degree of oral colonization by Candida species in 102 allogeneic stem cell transplantation recipients who were not receiving fluconazole prophylaxis. Of the 2071 serum samples, 98 (4.7%) yielded positive and 78 (3.8%) borderline results with a cut-off value of 0.5 ng/mL. One patient had IC. In this patient, 6 out of 9 serum samples were positive, the first one 49 days before Candida albicans candidemia. False-positive results occurred in 92 (4.4%) samples and in 54 (52.9%) patients. Use of valacyclovir and acyclovir was associated with false-positive or borderline results. The median Ag concentration of the true-positive results was significantly higher than the concentration of the false-positive results (1.60 versus 0.62 ng/mL, P