['The aim of this study was to examine the alterations in calcium and lipid peroxidation in red blood cells (RBCs) and serum samples of continuous ambulatory peritoneal dialysis (CAPD) patients. We also investigated the relationship between parathyroid hormone (PTH) and calcium homeostasis in this study.', 'For this purpose, routine blood counts and blood chemistry were analyzed by standard laboratory procedures in serum samples. The concentration of TBARS was measured in erythrocytes and serum samples. RBC calcium was measured by Fura-2AM in a spectrofluorometer.', 'In CAPD patients, hemoglobin, albumin, and high density lipoprotein cholesterol levels were lower, but glucose, very low density lipoprotein cholesterol, triglyceride, magnesium, PTH, sensitive C-reactive protein, and uric acid levels were higher than the controls. Thiobarbituric acid-reactive substance (TBARS) levels in RBCs and serum samples and cytosolic calcium in RBCs were all found to be significantly increased in CAPD patients compared to control subjects. Multiple regression analysis showed that RBC TBARS and serum PTH were the independent predictors of RBC calcium in our study.'] Do lipid peroxidation and parathyroid hormone influence the cytosolic calcium levels of erythrocytes in peritoneal dialysis patients?