Experimental studies were carried out on female Swiss albino mice to evaluate the possible role of: liver injury, urine inborn carcinogens and local irritation of bladder mucosa in the development of bilharzial bladder cancer. In mice, the liver and intestine are only involved by parasite, but the urinary bladder is spared. Mice with induced liver injury due to either: bilharzial infestation alone, hepatocarcinogens alone (2-naphthylamine (2-NA) or 2-acetylaminofluorene (2-AAF)), or both together, did not develop bladder tumors. Also, mice receiving 1% indole (a tryptophan precursor) either alone, or after bilharzial infestation, did not show any change in bladder mucosa. Conversely, the insertion of glass beads in the bladder induced carcinomas in 26.6% of mice after 70 weeks. The induction of bladder tumors by glass beads was enhanced by 2-AAF treatment (40%), but not by bilharzia infestation (25%), 2-NA (27%) or indole (27%). The urinary bladders with glass beads were invariably the seat of bacterial infection ( E-coli and gram + ve cocci) and showed epithelial hyperplasia and metaplasia.