We investigated antifungal susceptibility of 96 Candida species strains (37 strains of Candida albicans, 30 of Candida glabrata, 16 of Candida tropicalis and 13 of Candida parapsilosis) isolated from patients with invasive fungal peritonitis. Antifungal activity showed micafungin (MCFG), voriconazole (VRCZ)>itraconazole (ITCZ)>fluconazole (FLCZ). Judged by clinical breakpoints of Clinical and Laboratory Standards Institute (CLSI), FLCZ-resistant C. albicans, ITCZ-resistant C. albicans and VRCZ-resistant C. albicans were detected in the frequency of 5.4% (2/37), 21.6% (8/37) and 5.4% (2/37), respectively. We also retrospectively investigated the association of both antifungal susceptibility judged by CLSI breakpoints and clinical efficacy in 16 patients with invasive fungal peritonitis treated by injectable ITCZ. Clinical success and failure were obtained in cases of ITCZ MIC < or = 1 microg/mL and > or = 4 microg/ml, respectively. We conclude that we should re-consider CLSI breakpoints on ITCZ.