Cellular release of cytokines may be responsible for certain complications of extracorporeal dialysis including the increased susceptibility to infection found in dialysis patients. In order to study this further, we have evaluated the in vitro production of tumor necrosis factor (TNF) by peripheral blood monocytes (PBMC) to stimulation by lipopolysaccharide (LPS) from dialysis patients with end-stage renal failure (ESRF). The patients were subdivided into two groups according to the type of dialysis; those undergoing hemodialysis (HD) (N = 12) and those performing continuous ambulatory peritoneal dialysis (CAPD) (N = 9). Results were compared with those of controls taken from healthy laboratory staff (N = 7). The experiments show that the secretion of TNF by PBMC's in response to LPS is significantly augmented in patients undergoing HD when compared to those on CAPD (81.3 +/- 38.7 U/ml vs. 18.2 + 13.3 U/ml, mean +/- SD, P < 0.001); and controls (81.3 +/- 38.7 U/ml vs. 18.1 +/- 6.6 U/ml, P < 0.001). There was no significant difference between the CAPD group and controls. In vitro monocyte production of TNF fell following a single HD session (81.3 +/- 38.7 U/ml before HD and 50.5 +/- 28.7 U/ml after HD, P < 0.05). We conclude from this study that TNF release from PBMC's in vitro is augmented in patients with chronic renal failure receiving chronic HD but not in a similar group receiving CAPD. Interestingly, TNF release from monocytes collected immediately following a dialysis was suppressed.(ABSTRACT TRUNCATED AT 250 WORDS)