The composition of high-density lipoprotein (HDL) changes during inflammation; however, potential changes of HDL function during inflammation and the effects of acute phase proteins that are either on the HDL particles or in the serum have not been clarified. The concentrations of C-reactive protein (CRP), serum amyloid A protein (apoSAA) isoforms, lipids and apolipoproteins, and the activities of lecithin-cholesterol acyltransferase (LCAT) and paraoxonase (PON) were measured before and after laparoscopic cholecystectomy, in 12 patients with cholecystolithiasis to clarify the function of acute-phase HDL and the relationship between acute-phase proteins and HDL functions. Both acute-phase apoSAA (A-apoSAA) and CRP increased, reached their maximum levels 3-6 days after the operation, and then returned to preoperative levels after 2 weeks. In contrast, apolipoproteins and LCAT decreased reciprocally, reached their minimum levels 3-6 days after the operation, and returned to preoperative levels after 2 weeks. However, PON decreased 3-6 days after the operation, and remained low even after 2 weeks. At the nadir the mean activities of LCAT and PON were 56 and 76% of the preoperative levels, respectively. HDL-cholesterol or constitutive apoSAA did not change significantly. LCAT has been reported to be involved in reverse-cholesterol transport and PON to be preventive for lipid peroxidation of low-density lipoprotein in vitro. Thus, during the acute phase of inflammation, HDL may be altered to an atherogenic state due to a decrease in LCAT and PON activities. Therefore, this longitudinal analysis was carried out to determine whether HDL function is modified in a single episode of inflammation and thus may contribute to the occurrence of atherosclerotic disease in patients with chronic or recurrent acute inflammation.