Forty patients with acute calculous cholangitis had successful endoscopic drainage. Bile from nasobiliary drains and venous blood was collected at 0, 12, 24, 36 and 48 h after endoscopy. Endotoxin levels were measured by the chromogenic Limulus Amoebocyte Lysate assay. There was a significant reduction in both bile and serum endotoxin levels after endoscopic drainage (P < 0.001). Endotoxaemia occurred when bile endotoxin reached 10(3) EU/ml and rose exponentially beyond this threshold. Significant association was demonstrated between both bile and serum endotoxins to the clinical features of cholangitis (P < 0.05). No correlation was evident between serum endotoxin and the parameters of white cell count, serum bilirubin and alkaline phosphatase (r = 0.53, 0.00 and 0.00 respectively). Endoscopic drainage is effective in lowering bile and serum endotoxin levels and clinical signs and symptoms reliably predict endotoxaemia.