Inflammation plays a critical role in the pathogenesis of atherothrombosis. Our aim was to examine the association between plasma concentrations of inflammatory biomarkers and severity and outcome of acute brain ischaemia. Plasma samples were collected within 36 h of symptom onset in patients with acute brain ischaemia, and assessed by conventional ELISA kits for concentration of interleukin-6 (IL-6) and soluble intercellular adhesion molecule-1 (sICAM-1). Patients were assessed serially for stroke severity (National Institute of Health stroke scale) and outcome during follow-up (modified Rankin Scale, mRS; and Stroke Impact Scale-16, SIS). Patients (n = 113, 65% men, mean age 64 +/- 12 years) had a mean IL-6 concentrations of 5.1 +/- 5.0 pg/ml and sICAM-1 of 377 +/- 145 ng/ml. IL-6, but not sICAM-1, concentrations were strongly associated with stroke severity (P < 0.01 at all serial assessments). Ln-transformed IL-6 levels (per 1 SD) were associated with disability (mRS > or = 2, OR = 1.7; 95% CI 1.1-3.0) and poor physical function (SIS < or = 85, OR = 1.7; 95% CI 1.0-2.8). Further adjustment for baseline stroke severity, however, eliminated these associations. Our results suggest that high plasma concentrations of the inflammatory biomarker IL-6 but not sICAM-1 are associated with stroke severity and poorer functional outcome. IL-6 does not add, however, additional prognostic information for stroke outcome beyond that conveyed by the stroke severity.