Reliable markers for monitoring bladder tumor therapy are needed to evaluate treatment effectiveness. Thymidine kinase 1 (TK1) is an enzyme involved in DNA synthesis and therefore proliferation-dependent. Serum concentration of TK1 (STK1) correlates with malignancy in various types of cancer, thus reflecting treatment results. This study explores for the first time the use of STK1 concentration, both as a prognostic marker and to monitor the outcome of bladder carcinoma surgery. STK1 in 56 bladder carcinoma patients was measured pre-operatively, and post-operatively at 1 week and 1, 3, and 6 months, using an immune ECL dot blot assay. An anti-TK1 chicken IgY antibody was used to determine STK1 concentrations. Mean pre-operative STK1 of bladder carcinoma patients was significantly higher than that of healthy individuals, with no overlap of individual values. STK1 concentrations increased significantly with tumor stage (I-III) and T-values (T1-T2), but not tumor grade (G1-G4). STK1 gradually declined, being 66% lower after 1 week. STK1 reached the level of healthy controls at 1 month and remained there for at least 6 months, post-operatively until this study ended. Since STK1 concentration correlates with tumor stage, degree of invasion and metastasis, and monitors the surgical outcome, it can be a reliable index to diagnose and determine prognosis in post-operative bladder carcinoma.