Malnutrition is a serious and common problem among patients dialyzed with peritoneal dialysis. Simple and reproducible methods of nutritional status assessment are needed for early problem identification to prevent and treat this complication. The aim of the present study was to evaluate the usefulness of albumin serum concentration and normalized protein catabolic rate (NPCR) derived from urea kinetic modeling session to assess the clinical status of ESRD patients treated with Continuous Ambulatory Peritoneal Dialysis (CAPD). Statistically significant, negative correlations between NPCR and hospitalization rate (r = -0.307; p < 0.05) and co-morbidity score (r = -0.429; p < 0.001) as well as statistically higher NPCR in the group of patients who survived the whole study period (0.82 vs. 0.74 in Non-Survivors; p < 0.01) support the value of this marker as an indicator of clinical status of peritoneal dialysis patients. Significant, negative correlations between serum albumin level and co-morbidity score (r = -0.379; p < 0.05), peritonitis rate (r = -0.359; p < 0.05) and hospitalization rate (r = -0.601; p < 0.005) were also found. Low absolute values of NPCR for the whole population as well as significant, positive correlations of this marker with dialysis adequacy parameters with concomitant lack of such correlations for albumin indicate, that NPCR as a nutritional marker should be interpreted with caution, and always regarded to the calculation method.