We examined the indicators of oxidant/antioxidant (O/A) balance in the blood of, 118 women with chronic pyelonephritis. (PN), aged 18 to 69 years (mean 36.0 +/- 7.9 years) and 30 conventionally healthy donors: 82 (69.5%) of patients had the recurrent PN, 36 (30.5%) of women had the sporadic PN. The malondialdehyde in serum, ceruloplasmin, transferrin and the number of sulfhydryl groups, which allowed to calculate the index of oxidative stress (IOS) were included into the complex research of O/A balance. IOS was significantly increased in patients with recurrent PN 4.27 2.06 vs. 2.30 +/- 1.06 for sporadic PN (P < 0;001). It allowed us to conduct the multivaiate analysis using binary logistic regression. The analysis demonstrated alhigh quality (>80 %) of regression model chi2 = 74.3; P < 0.001, odds ratio (OR) = 7.5, 95% CI 3.3-7.1. We have created an additional examinational sample to confirm the adequacy of this model which included the test results of 23 pa- tients with acute PN in 6 (26%) of them have developed recurrent PN. We defined a high quality of examinational model chi2 = 11.2; P = 0.0008, OR =3.34, 95% CI 1.3-10.3. The optimal criteria for IOS was > 3, sensitivity 100%, and for specificity 94%. Thus, for the prediction of recurrent PN can be evaluated the IOS. The development of recurrent PN can be predicted with probability 97.6% if value of IOS > 2.5; this will optimize the rehabilitation program of patients Vith acute PN.