Janthinobacteriun lividum was isolated from wet silk thread whose color became bluish-purple7, 8). This bacterium produced large amounts of bluish-purple pigment on some media containing amino acids, such as Wakimoto medium. The pigment was extracted with methanol and was identified as a mixture of violacein and deoxyviolacein. This pigment could be used to dye not only natural fibers like silk, cotton and wool, but also synthetic synthetic fibers like nylon and vinylon, and generally gave a good color tone. The shade depended on the material. Silk, cotton and wool showed a bluish-purple color, nylon a dark blue color, and acetate a purple color. Dyeing could be performed by a simple procedure consisting of either dipping in the pigment extract or boiling with the bacterial cells. By changing the dipping time and the temperature of the dye bath, shades ranging from light purple to deep bluish-purple could be selected. The color fastness of the dyed material was about the same as that materials dyed with vegetable dyes, but the color faded easily when the material was exposed to sunlight. However, since the pigment can be mass-produced by culturing, if these shortcomings could be overcome, the dye may become promising. The pigment displayed an antimicrobial activity against phytopathogenic fungi like Rosellinia necatrix which causes white root rot of mulberry 7). It could also be used as a bio-fungicide.