Sepsis is a major factor in the high mortality and morbidity following diagnostic and therapeutic procedures in patients with obstructive jaundice. The reasons for this increased susceptibility to infection are not fully understood. We therefore observed prospectively changes in immunological status of patients with obstructive jaundice in the perioperative period and studied immunological effects of perioperative arginine therapy. The results showed that there was a significant reduction in interleukin 2 (IL-2) production, interleukin 2 receptor (IL-2R) expression and lymphocyte response to phytohemagglutinin (PHA) mitogen in patients with obstructive jaundice compared with normal controls. After operation, the immune suppression in patients with obstructive jaundice was more significant. Arginine is a known T lymphocyte stimulator. Perioperative supplement with arginine significantly enhanced the immune function of patients with obstructive jaundice, the mechanism being related to increased IL-2 production and IL-2R expression.