Erythrocyte, serum and urine ferritin concentrations were evaluated in 20 patients suffering from transitional cell carcinoma of the urinary bladder and in 20 healthy men. No clinical or biochemical signs of liver disorders, chronic inflammatory states or infections were present in both the patients and the controls. Our results showed no significant difference in the erythrocyte ferritin concentration in both groups. On the contrary there was a statistically significant difference in mean serum (p less than 0.05) and urine (p less than 0.01) ferritin concentration between the two groups. The mean serum ferritin concentration in the patients was 102.23 +/- 63.38 ng/ml while it was 258.41 + 250.68 ng/ml in normal subjects. The mean urine ferritin concentration was 6.30 +/- 5.35 ng/ml in normal subjects and 22.66 +/- 25.59 ng/ml in patients with bladder cancer. Our data seem to demonstrate that the assessment of the ferritin either in the serum or preferably, in the urine, could become an interesting tumoral marker for bladder cancer.