ABSTRACT: Bladder cancer is one of the most common disease treated by urologist1 .In the united state, bladder carcinoma is the forth most common cancer in men after prostate, lung and colorectal cancer. In women it is the eighth most common cancer. Bladder carcinoma is more than 2.5 times common in men than in women and accounts for 2.9% of all cancer death in men and 1.5% in women. Objectives: studying the role and efficacy of reduced glutathione as a tumor marker in diagnosis and follow up patients with urinary bladder carcinoma. Patients and methods: Fifty seven patients with proved carcinoma of the urinary bladder were studied for the change in their GSH(reduced glutathione) levels in the blood. The studied patients were 47 males and 10 females and the control group was 30 persons of different ages and sexes, those patients were complaining from hematuria, the diagnosis of bladder carcinoma was made by Histopathological study of the biopsy taken from the bladder during cystoscopy. All patients had transitional cell carcinomas and no squamous, adenocarcinoma or other types had been found. The study had evaluated the effect of smoking ,sex, residency, tumor size and grade on the level of GSH in the blood. The mean age of the patients was 52.5 years ,44 patients (77%) were smokers ,13 patients(23%) were non smokers.31 patients(54%) had history of urinary stone. Two patients(3.5%) had family history of carcinoma of the bladder in the first degree relatives. Four patients(7%) had second degree relatives for bladder cancer.47 patients(82%) were males while 10 patients (18%) were females, male to female ratio was 4.7:1.The highest percentage of the patients 54% were from the periphery of ALmuthana Governorate while 46% were from the centre. 68.4% had Grade II, 17.5% had Grade I, and 14.1% had Grade III tumor. Regarding tumor size; 40 patients(70%) less than 2 cm, 12 patients(21%) between 2 and 5 cm[2-5cm],and 5 patients (9%) had tumor size more than 5cm. Results: The study shows that carcinoma of the urinary bladder causes significant decrease in the blood levels of reduced Glutathione(GSH) in both sexes, with females had relatively higher levels than males. Smoker patients had lower GSH levels than non smokers, Urban patients had lower blood GSH levels than rurals. Regarding the grade and size of the tumor, the study revealed that blood level of reduced Glutathione increases with the increase of the tumor grade while decreases with the increase in the tumor size.