The authors have carried out an examination and treatment of 25 pregnant women with pyelonephritis, which arose during different terms of pregnancy, using a "stepwise" antibiotic therapy with a transition to suppressive therapy until the end of pregnancy. A comparison group was made up of 20 pregnant women with pyelonephritis, who were not preseribed suppressive therapy. The absence of recurrences in 95 % of the gravidas of the basic group has been established, regardless of the drug used for suppressive therapy. In the comparison group of women who were not prescribed suppressive therapy until the end of pregnancy, the absence of the relapse was observed in 11 % of pregnant women, which was significantly different.