Several risk factors have been suggested for transitional cell carcinoma (TCC) of the bladder (BC). Since itseems that some factors have more prominent role over the others in our region, we conducted the present casecontrolstudy with 692 bladder cancer (BC) patients versus 692 healthy controls (262 women versus 1,122 menin total) matched on the basis of gender and age (±5 years). The enrolled cases had confirmed TCC of bladder.To gather data, we exploited a questionnaire filled up in face-to-face interviews. We classified different factorsin four categories as follows: 1-dietary factors; 2-history of underlying diseases; 3-lifestyle; and 4-occupational/chemical exposures. Among dietary factors, pickles (P= 0.04) and vegetables (P= 0.001) had protective effects.In the second group, histories of all evaluated diseases were accompanied by increased risks for BC. Among lifestyle factors, cigarette smoking (P= 0.0001), opium use (P= 0.0001), history of excessive analgesic use (P= 0.0001)and hair dye use (P= 0.02) had significant correlations with BC. However, none of the occupational exposureswas associated with BC. One may conclude that some factors such as opium use may have a more important rolein developing BC in our region. Nonetheless, we should categorize occupations based on their definite exposureto chemicals for conducting further studies.