Arborcandin C is a novel antibiotic with potent antifungal activity that inhibits 1,3-beta-glucan synthase in fungi. We examined spontaneous Saccharomyces cerevisiae mutants which are selectively resistant to arborcandin C and revealed that a single amino acid replacement in Fks1p of Asn(470) with Lys or of Leu(642) with Ser confers selective resistance on Fks1p mutants.