Background: Heat shock proteins (HSPs) play essential roles as molecular chaperones in tells to assist in the repair of degenerated proteins. The expression of HSPs in polymorphonuclear leukocytes (PMNLs) following insult has not been delineated. The objective of this study was to clarify the serial changes in HSP expression in PMNLs from trauma patients. Methods: Fifty severely injured patients (mean Injury Severity Scare of 31.8 +/- 10.8) and 17 healthy volunteers were included as study subjects, flood samples were serially obtained at three time points: days 0 to 1, days 2 to 5, and days 6 to 1J after the trauma event, We measured expressions of HSP27, HSP60, HSP70, and HSP90 in permeabilized PMNLs by flow cytometry using a monoclonal antibody generated against each HSP and fluorescein isothiocyanate-conjugated antimouse immunoglobulins as secondary reagents. We also evaluated the expression of HSP70 mRNA in PMNLs by Northern blot hybridization and the expression of HSP70 in PMNLs by fluorescence microscopy. Results: Expressions of HSP27, HSP70, and HSP90 in PMNLs from trauma patients were significantly greater than in PMNLs from healthy volunteers in ail three periods (days 0-1, days 2-5, and days 6-14). The expression of HSP60 in HNLs from trauma patients was significantly greater than normal expression on days 2 to 5 and days 6 to 14, The values for HSP27, HSP60, and HSP70 on days 2 to 5 were significantly higher than those on days 0 to 1, The expression of HSP70 mRNA in PMNLs was significantly enhanced for as long as 2 weeks after trauma compared with that in normal volunteers. Conclusion: Severe trauma causes demonstrated enhanced expression of HSPs in PMNLs during the acute phase. This enhanced expression of HSPs may regulate PMNL functions.