Urine and serum concentrations of interleukin (IL)-6 and IL-8 were determined in 43 women with acute pyelonephritis caused by Escherichia coli. Urine and serum samples were also collected 2 weeks after the infection and during a subsequent episode of cystitis (n = 8) or asymptomatic bacteriuria (n = 8). Concentrations of IL-6 and IL-8 were related to the expression of 5 virulence markers of E. coli and glomerular filtration rate (GFR) after pyelonephritis. Patients with acute pyelonephritis had elevated urine and serum IL-6 and IL-8 levels as compared to 37 healthy women (IL-6: p < 0.001 in both cases, and IL-8: p < 0.001 in both cases). Patients infected with E. coli producing hemolysin and/or cytotoxic necrotizing factor (CNF) had significantly higher IL-6 levels in serum during acute pyelonephritis as compared to patients infected with strains without the ability to produce these factors (p = 0.0025 and p = 0.0154, respectively). Patients who had high concentrations of IL-8 in urine during acute pyelonephritis had lower GFR at follow-up as compared to patients with lower levels of IL-8 in urine (r = -0.48, p = 0.0123). In conclusion, acute pyelonephritis is accompanied by elevated urinary and serum IL-6 and IL-8 levels. Bacteria producing hemolysin and CNF seem to induce higher concentrations of IL-6 in serum. The secretion of IL-8 from renal cells may participate in the initiation and maintenance of renal inflammation which in turn may influence renal function.