The release of circulating isoforms of selectin- (L-selectin, ELAM-1) and immunoglobulin-type- (ICAM-1) adhesion molecules, responsible for accumulation of leukocytes at sites of tissue injury was studied in CSF and serum of 21 patients with bacterial meningitis and in healthy subjects. Their concentrations were compared with the intrathecal leukocyte recruitment and release of inflammatory cytokines. In contrast to serum concentrations of the leukocyte-derived adhesion molecule, sL-selectin, serum concentrations of endothelial-derived adhesion molecules, sELAM-1 and sICAM-1, were significantly increased in meningitis. No intrathecal synthesis of these adhesion molecules was observed. Serum levels of sELAM-1 were associated with extent of CSF pleocytosis and with concentrations of proinflammatory cytokines IL-1beta and TNF alpha in CSF, but not in serum. Therefore, expression of endothelial adhesion molecules i.e. ELAM-1 may be responsible for the massive intrathecal recruitment of potentially harmful leukocytes in patients with bacterial meningitis. Intrathecally released proinflammatory cytokines may represent the inducing signals for their endothelial upregulation.