The effect of anilazine on growth, respiration and enzyme activity of E. coli has been studied. Anilazine delays the growth of E. coli by prolonging the lag period. It inhibits glucose oxidation by 60% and succinate oxidation by 100%. It also inhibits in vitro succinic dehydrogenase activity. It seems that the inhibition of E. coli by anilazine is because of inhibition of respiratory enzymes.