Transitional cell carcinoma of the bladder carries a high rate of local recurrence and 15%-30% of the cases progress to advanced stages of the disease. The multiple forms of the tumor make it difficult to find reliable diagnostic elements of tumor evolution and some authors have advocated the use of tumor markers for the diagnosis and follow-up of malignant bladder tumors. This study was conducted to determine the biological behaviour of the HCG beta subunit it transitional cell carcinoma of the bladder. One hundred patients were entered into the study; the control group comprised 30 healthy subjects and the patient group comprised 70 cases of transitional cell carcinoma of the bladder. The results showed the HCG beta subunit increased with the size and degree of tumor infiltration, although the data were not statistically significant. Similarly, analysis of the degree of tumor differentiation/non differentiation provided no statistically significant data.