The monitoring of PSA values following prostatectomy demands for the use of highly sensitive tests with low detection level. The possibilities to use the EIA Dialab test to monitor the PSA values after radical prostatectomy for early detection of persistent diseases were investigated by determining the biological detection limit (BDL) in serum of patients who unrewent cystoprostatectomy. The obtained values were compared with Abbott Imx test for PSA determination. A good correlation between the two studied methods was establisahed, r = 0.9827 with the regression curve Yx = 0.20463 + 0.96277. Test indicated that there was no significant difference (p < 0.001) between the investigated methods.