A species of Verticillium, an imperfect fungus isolated from a basidiocarp of Coltricia cinnamomea, produced a new antibiotic, verticillin A. Verticillium sp. strain TM-759 was fermented in a medium containing glucose, peptone, and NaCl, with the mycelium extracted using acetone and ethyl acetate. Verticillin A was purified and characterized as C₃₀H₂₈O₆N₆S₄ (with crystal solvents), showing spectral features (IR, NMR, mass spectrum, circular dichroism) indicative of a disulfide-bridged diketopiperazine system; alkali treatment yielded diindolyl-(3,3'), suggesting it belongs to the gliotoxin group. Verticillin A acetate exhibited antimicrobial activity against Gram-positive bacteria (e.g., Bacillus subtilis PCI 219 MIC 2 mcg/ml, Staphylococcus aureus FDA209P MIC 2 mcg/ml) and Mycobacterium tuberculosis H37Rv (MIC 1 mcg/ml), but not against Gram-negative bacteria or fungi. It had a cytotoxic ED₅₀ of 0.2 mcg/ml against HeLa cells, antitumor activity against Ehrlich ascites carcinoma, weak antiviral activity against poliovirus, and an intraperitoneal LD₅₀ of 7.6 mg/kg in mice.