In the course of our screening for new antibiotics, a new compound, viridomycin F (1, Fig. 1), was isolated from a culture broth of Streptomyces sp. K96-0188. Compound 1 is a complex of iron and /^-substituted onitrosophenol trimer and showed moderate insecticidal and nematocidal activities. Several iron complexes of ^-substituted 6>-nitrosophenols, viridomycin A (2)x ~3) and E4), actinoviridin (3)5), 4-hydroxy-3-nitrosobenzamide ferrous chelate (4)6), and ferroverdin (5)7?8), have been isolated as green pigments from actinomycetes. As for biological activities, only moderate antibacterial activity of 2 against some Gram-positive bacteria has been reported1'3). In this report, we describe the characteristics of the producing strain and the fermentation, isolation, physico-chemical properties, structure elucidation, and biological activities of 1.