Fusarium wilt of banana (Musa sapientum) caused by Fusarium oxysporum f. sp. cubense (FOC) is one of the most economically devastating plant diseases in the world (Hwang and Ko 2004). This disease is difficult to control with pesticides, therefore many bio-control strategies have been researched and developed (Cao et al. 2005; Nel et al. 2006; Sivamani and Gnanamanickam 1988). Whilst screening for potential antimicrobials from banana, we found a mycoparasite in dual culture with FOC. Fungus isolate ES-1 was isolated from pseudostem tissue of healthy banana plant in the Wu River watershed (Nantou Country, Taiwan), and cultured on potato dextrose agar (PDA) in 8.5 cm Petri plate at 28°C with alternating light and dark periods of 12 hours each. The colony was white, cottony, tortuous branching at the edge, covered the plate in 10 days. The hyphae became melanized after 7 to 14 days culture and the surface became loosely woolly and grainy. Superficial and immersed pycnidia formed in the grayish grains on colony after culture for 5 to 7 weeks, black rind outside and pale-yellow inside, ostiolate, 3-4 mm in diameter, with 1 to 5 beaks (2-6 mm long) on the upside (Fig. 1a), releasing dark-brown conidial mass. Conidia were hyaline, filiform to slightly curved, truncated at one end, (10-)15-20(-22) × 1.5- 2.0(-2.2) μm, 16.0 × 1.8 μm on average (Fig. 1b).