Neutrophil accumulation in the graft kidney is a feature of cellular rejection and bacterial infection. The cellular infiltration is mediated by the local production of chemoattractant factors. The aim of the study was to analyze levels of IL-8 in renal graft recipients during and after episodes of acute renal rejection and urinary tract infection (UTI). A total of 50 renal graft recipients, including 10 with acute graft rejection (Group I) and 20 with UTI (Group II) were studied. Urine and serum levels of IL-8 were determined in patients of Group I before and after 7 days of antirejection therapy and in patients of Group II before and after 2 weeks of antimicrobial therapy. Results were compared with group of 20 patients with stable renal function and a group of 25 healthy people. IL-8 was determined by ELISA technique. The level of IL-8 in urine (uIL-8) was elevated in patients with acute graft rejection and uIL-8 decreased after antirejection treatment (772 +/- 241 pg/mg cr. vs 140 +/- 50 pg/mg cr.; p < 0.01). In 13 patients UTI was asymptomatic and 6 patients had an acute pyelonephritis. The level of uIL-8 was elevated in all patients with UTI and decreased after antimicrobial therapy. Levels of uIL-8 during acute pyelonephritis were significantly higher (p < 0.01) than in patients with asymptomatic bacteriuria (2582 +/- 950 pg/mg cr. vs 804 +/- 225 pg/mg cr.) Urine levels of IL-8 were lower in patients infected by Gram-positive Cocci as compared to patients infected by Gram-negative organisms. Patients with higher concentrations of serum creatinine during UTI had high urine levels of IL-8. Serum levels of IL-8 in patients of Group I and Group II were comparable with patients with stable graft function although they were higher than in control group. Elevated urinary secretion of IL-8 in acute rejection and UTI suggests a role of IL-8-neutrophiles system in in the pathogenesis in both inflammatory complications after kidney transplantation. Urine level of IL-8 was correlated with clinical symptoms of UTI.