Introduction. Bladder cancer is one of the most common urinary system malignancies. There are contraversies regarding priority and intensity of its risk factors according to the health behavior and life style of different societies. Therefore it seemed necessary to investigate the risk factors of bladder cancer in Iranian society. Methods. A case-control study was done in 284 bladder cancer patients and hospitalized controls. The case group was 142 primary bladder cancer patients based on pathological results and control group was 142 patients selected randomly from medical-surgical wards, excluding oncologic and urologic patients, also those had hematuria in their urine analysis. Two groups were matched according to their sex, age and their hospitalization site. The data was collected via interview and questionnaire. Results. The mean age of patients at diagnosis time was 64.4 years. The bladder cancer frequency in men was 3.7 times more than women. There was a significant relationship between bladder cancer and educational level, the place of residence, cigarette smoking, tea drinking, and consumption of high fat foods, frequent and chronic urinary infection and family history of cancer. Discussion. In this study many known bladder cancer risk factors were approved again. The relation between bladder cancer and opium addiction needs further investigation. It is recommended that early detection, screening tests such as urine analysis should be done in high risk individuals.