['To investigate the reason for increasing norepinephrine (NE) levels reported in continuous ambulatory peritoneal dialysis (CAPD) patients.', 'Norepinephrine was measured in the plasma and peritoneal dialysate of CAPD patients (n = 22) and in the plasma and the urine of healthy subjects (n = 20). It was also measured in the plasma of patients with chronic renal failure (CRF) (n = 15) and patients on hemodialysis (HD) (n = 15).', 'It was found that NE was increased in CAPD patients compared with healthy individuals (687+/-221 pg/mL vs 199+/-25 pg/mL, p < 0.01). The daily removal of NE from the peritoneum of CAPD patients was lower compared with the amount of NE excreted in the urine of healthy subjects. Plasma NE increased after infusion of peritoneal dialysate. In 15 new patients on CAPD, it was found that NE plasma levels increased from 329+/-67 pg/mL before initiation of dialysis, to 584+/-173 pg/mL after 12 months of treatment (p < 0.01). Finally, plasma NE in CAPD patients (687+/-221 pg/mL) was significantly higher compared with the already increased levels in patients on HD or with CRF (406+/-143 pg/mL and 378+/-142 pg/mL, respectively).'] Is continuous ambulatory peritoneal dialysis responsible for an increase in plasma norepinephrine?