In patients with chronic renal failure, whether they have had hemodialysis or not, the specificity of some of the serum tumor markers for the diagnosis of the corresponding tumors is decreased while others remain as valuable as they are in patients with normal kidney function. The detection of tumor markers is extensively used for the diagnosis of corresponding tumors. It has been recently shown that some tumor markers are higher in patients with chronic kidney disease (CKD) than in the normal population. The effects of renal function and hemodialysis were examined on serum levels of some of the tumor markers including CEA, CA199, CA125, AFP, CA153, CA724, CYFRA21-1, NSE, SCC-Ag, PSA, and fPSA. The 232 non-dialysis patients with CKD and 37 chronic uremic patients treated with maintenance hemodialysis were enrolled in this study. The 232 non-dialysis patients were divided into three groups according to their Ccr. In group 1, Ccr was ≤25 mL/min. In group 2, Ccr was between 25 and 50 mL/min. In group 3, Ccr was ≥50 mL/min. The male patients were also divided into three groups to compare the serum levels of PSA and fPSA among the three groups. Nine tumor markers in 37 uremic patients were tested. For comparison, 37 non-dialysis patients with similar Ccr of the same age and gender served as controls. There existed significant differences in serum levels of CEA, CA199, CYFRA21-1, NSE, and SCC-Ag among different Ccr groups and the markers bore a negative correlation with Ccr. There were no significant differences among the three groups in the serum concentrations of CA125, AFP, CA153, CA724, PSA and fPSA. The serum levels of CA125 and NSE were significantly higher (P199, CYFRA21-1, NSE, CA125 and SCC-Ag for the diagnosis of the corresponding tumors was decreased while serum AFP, CA153, CA724, PSA and fPSA were as valuable as they were in patients with normal kidney function. Hemodialysis further increased the serum level of CA125 and NSE.