To examine whether changes in leukocyte adhesion properties occur during stroke, we measured circulating serum intercellular adhesion molecule 1 (cICAM-1) levels and neutrophil adhesion in acute stroke, patients at high risk of stroke, and in matched controls. Levels of cICAM-1 were significantly lower in the stroke group (186.2 +/- 15.6 ng ml-1) compared to controls (257.7 +/- 24.8) and risks (257.7 +/- 16.5). Neutrophil adhesion was significantly higher in the stroke group (23.6 +/- 4.3%; n = 14) compared to controls (9.7 +/- 2.3%; n = 12) and risks (12.7 +/- 2.5%; n = 13). These data suggest that changes in leukocyte adhesion dynamics are occurring in acute stroke.