Six new α-pyrone derivatives, named cladobotrins I-VI (1-3, 5, 10, 11), and a know one, rosellisin aldehyde (6), were isolated from the culture broth of a mycoparasitic fungus, Cladobotryum varium NEES et DUBY (=Didymocladium ternatum BON.). Their structures were established by spectroscopic methods including two-dimensional NMR techniques. Among the compounds obtained, three α-pyrone derivatives, having a formyl group at the C-5 position, showed inhibitory activity against the mycelial growth of a fungus, Ganoderma lucidum (FR.) KARST., the fruit bodies of which are used as the oriental crude drug "Lin-Chi".