The estimation of CAPD efficacy presents a complex problem in the patients treated by this method. The most important parameters are: clinical indications, biochemical parameters, Kt/v, PCT, PET indexes, and others. Numerous factors may influence CAPD efficacy. Peritonitis, particularly the frequent episodes, significantly affects permeability and ultrafiltration capacity of the peritoneal membrane. The aim of this paper is to investigate the peritonitis incidence and its influence on some parameters of CAPD efficacy. Forty-four CAPD patients of both sexes, aged 55.7 +/- 13.5 yrs, dialysis duration 19.6 +/- 15 months, were studied. The influence of peritonitis incidence was studied using urea, creatinine, hemoglobin, hematocrit parameters and K t/v, PET indexes. Statistically significant low K t/v values were found in the patients who had four or more peritonitis episodes. Our results, as well as those in the literature, indicate that frequent peritonitis episodes significantly decrease the peritoneal membrane permeability.