Such HLA phenotypes as A3B35 and A9B35 occur most frequently in patients with chronic pyelonephritis (CP). In these phenotypes there are most pronounced changes in the lipid phase of red cell membranes and renal tissue. The above changes of blood cell cytomembranes and renal tissue can be used as diagnostic criteria of inflammation activity in pyelonephritis while the HLA antigens are helpful for detection of CP risk groups.