Transformation of the azodyes, frequently used in food and pharmaceutical preparations, may lead to possible health hazards. The role played by enteropathogens in the azoreduction has not yet been investigated. Shigella dysenteriae (Type 1) isolated from human intestine has been shown to reduce different azocolorants. Some properties of the enzyme system involved in this reductive process have been studied. Azoreductase activity was assayed by monitoring the decrease in color intensity at the absorption maxima of different dyes. The azoreductase obtained from the cell-free extract of S. dysenteriae (T 1) was oxygen-insensitive and could use Ponceau SX, Amaranth, Orange II and artrazine in varying degrees. Both NADH and NADPH could serve as electron-donors, NADH being the more effective one. The activit of this enzyme was markedly stimulated by flavins Azoreductase activity could be induced 1.5-5 fold by growing the bacteria in presence of some azodyes. Tartrazine and Amaranth were better inducers than others tested.