Cultures of endophytic fungi collected in the Guanacaste Conservation Area of Costa Rica were screened for antifungal activity. CR377, a new pentaketide antifungal agent, was isolated from the culture broth of a fungus, CR377 (Fusarium sp.), that showed potent activity against Candida albicans in this assay. The structure of CR377 was established using 1- and 2-D NMR and HRFABMS.