In order to investigate cytokine productions in patients undergoing continuous ambulatory peritoneal dialysis (CAPD), we studied the production of interleukin (IL)-1 β, -6 and interferon (IFN)-γ by cultured peripheral blood mononuclear cells (PBMC) in peritonitis-free CAPD patients. The correlation of cytokine production with plasma parathyroid hormone (PTH) and albumin levels was also evaluated. While the release of IL-1 β was not markedly different from controls release of IL-6 from 24-hour cultured PBMCs was significantly greater than that of controls, (Mean ± S.D., IL-6: 2186.8 ± 1217.9 pg/ml, vs 1516.3 ± 767.9, P <0.05). The addition of lipopolysaccharide (LPS, 10 µg/ml, significantly stimulated IL-1 β and -6 production of PBMCs in CAPD patients and controls, compared to an unstimulated condition. The LPS-induced IL-1 β production was also not markedly different from controls, whereas LPS-induced IL-6 production was significantly higher than controls (IL-6: 13,220.7 ± 7177.4 vs 7411.4 ± 1236.9, P <0.05). However, the percentage increases of IL-6 production stimulated with LPS in CAPD patients were not significantly different from controls (p > 0.05). No difference of baseline IFN-γ was detected between CAPD patients controls, but phytohemagglutinin (PHA, 10 µg/ml)-stimulated IFN-γ release was significantly higher in CAPD patients than controls (2425.9 ± 1565.0 pg/ml vs 1364.0 ± 755.1, P <0.05). There was no significant correlation between PTH and, IL-1 β, serum albumin level and LPS-stimulated IL-6 production (r = 0.54, P <0.05). In conclusion, CAPD seems to partly induce activation of PBMCs with an enhanced release of IL-6 and IFN-γ, and CAPD patients with higher serum albumin levels tend to show higher IL-6 production in immune response.