From the point of allergy, the authors studied on the production of cholelithiasis and cholecy-stitis and the results obtained were as follows: 1. By agglutination reaction with the antigen of E. coli (O-6) isolated from human faeces and the normal human serum, it was found that the aggulutin in titer was so low in the infant and the titer rising up rapidly with the age to 10 years old. Thereafter the titer is coming close gradually to that of the adult. These facts suggest that tha natural sensitization by E. coli exists in the human being and it may be strengthened gradually with the age. 2. Natural sensitization by E. coli was also found in the normal rabbit and it was also observed that the natural sensitization was enphasized by the oral administration of E. coli. 3. The disturbance of the liber may produce dysbacteria of the intestinal flora and the dysbacterial condition of the intestinal flora and the disturbance of the liber-function may emphasize the natural sensitization by oral administration of E. Coli and moreover it may be an important factor in the appearance of orally administered E. Coli in the bile. 4. The bile of gastro-ulcer showihg no precipitation reaction with anti-E. Coli rabbit serum was mixed with E. Coli (O-6) and after 24 hours' incubation at room temperature the bile showed positive reaction with anti-E. Coli rabbit serum. 5. The remarkable growth of E. Coli was found in the group of rabbits blocked the bile-duct injected E. Coli via bile-duct, however no growth of bacilli was observed in the normal rabbits; moreover, the bile in the former cases showed positive reaction with anti-E. Coli rabbit serum. 6. Electromicroscopic findings show that the breaking or dissolution of cell wall or cell membrane and the prolapse of the protoplasma of E. Coli at the high concentration of Desoxycholic acid or glycodesoxycholic acid. 6. The gall-bladder isolated from the guinea pig administered orally E. Coli and showing high aggulutinin titer showed anaphylactic reaction by Schultz-Dale technique. Anaphylactic reaction of the isolated gallbladder in the guinea pig sensitized with anti-E. Coli rabbit was alse demonstrated and also the desensitization phenomenon was clearly demonstrated with the addition of the same antigen. These results suggest that allergic or anaphylactic reaction in the gall-bladder with antigen-antibody system of the components of E. Coli might be existed.