Objective. Increased serum pro-inflammatory cytokine levels are associated with an increased mortality rate in end-stage renal disease (ESRD) patients. Statins decrease cardiovascular mortality and serum C-reactive protein (CRP) levels in hemodialysis patients. As the anti-inflammatory effect of statins has not previously been studied in peritoneal dialysis (PD) patients with a non-inflammatory status, we wanted to investigate the anti-inflammatory effect of simvastatin in these patients. Material and methods. Forty-eight PD) patients were randomly allocated to either simvastatin treatment (n = 2 5) or placebo (n = 23). Patients in the active-treatment group received simvastatin 20 mg/day for I month. At baseline and after I month of treatment, blood samples were drawn and high-sensitivity CRP, interleukin-6, tumor necrosis factor (TNF)-alpha and plasma lipid profiles were determined. These parameters were compared between the groups at baseline and at the end of the study period. Results. Twenty-five subjects in the treatment group and 20 in the placebo group completed the study. Three patients in the placebo group were excluded from the study due to the occurrence of bacterial peritonitis during the study period. Clinical characteristics and baseline parameters were similar in both groups. Serum total and low-density lipoprotein cholesterol levels, and triglyceride and serum TNF-alpha levels decreased significantly compared to baseline in the treatment group; there were no corresponding differences in the placebo group. Conclusions. Simvastatin decreased the serum TNF-a level in PD patients with a non-inflammatory status. A decrease in the TNF-alpha level could be one of the possible mechanisms of the anti-atherogeneic effect of simvastatin. We suggest that different treatment strategies aimed at decreasing serum cytokine levels could be evaluated to decrease cardiovascular morbidity and mortality in the dialysis population.