In clinical cases of cholera Vibrio cholerae grows, multiplies and undergoes lysis in the intestine. Although there are numerous works on the enzymatic make-up of V. cholerae, there is hardly any literature on the effect of different gastrointestinal enzymes on the toxin in bringing about the signs and symptoms of the disease. According to one school of thought, cholera toxin plays an important role in the pathogenesis of the disease.The effects of gastrointestinal enzymatic extracts of rabbit and pure gastrointestinal enzymes on the toxin were studied. The resultant degraded products were tested for their ability to produce cholera in young rabbits.When the toxin was treated with adult-rabbit enzymatic extract, it was degraded and the choleragenic property was lost, but this was not true of toxin treated with young-rabbit enzymatic extract. This might explain the resistance of the adult rabbit to the infection. The choleragenic property of the toxin was also lost when it was treated with lipase of phosphorylase but not with trypsin or pepsin. The lipopolysaccharide portion of the toxin was shown to be important from the point of view of pathogenesis.