A new epidithiodioxopiperazine compound named verticillin G along with the known compound verticillin D has been isolated from the mycelium of liquid fermentation cultures of a fungal strain Bionectra byssicola F 120. The structure of verticillin G was determined on the basis of MS and NMR data. Verticillin G inhibited the growth of Staphylococcus aureus including methicillin-resistant and quinolone-resistant S. aureus with MIC (microg/ml) of 3-10.