The aim of this study was to find the correlation between serum p53 and carcinoma of the bladder and to investigate whether serum p53 protein can be used as a tumor marker for p53 gene alteration. The study included patients with carcinoma of the bladder and controls. Serum p53 protein estimation was done with an ELISA kit. There were 23 patients with superficial and 17 with invasive carcinoma. The median serum p53 was 31.5 U/ml in superficial and 41 U/ml in invasive cancer. This was significantly higher than the mean value (16.4 U/ml) of controls. Serum p53 rises in patients with carcinoma of the bladder and correlates with the grade of the disease . It can therefore be used as a tumor marker for bladder cancer.