We aimed to quantify the association of blood interleuldn-6 (IL-6) concentrations with poor outcome after stroke and its added predictive value over clinical information. Meta-analysis of 24 studies confirmed this association with a weighted mean difference of 3.443 (1.592-5.294) pg/mL, despite high heterogeneity and publication bias. Individual participant data including 4112 stroke patients showed standardized IL-6 levels in the 4th quartile were independently associated with poor outcome (OR = 2.346 (1.814-3.033), p <0.0001). However, the additional predictive value of IL-6 was moderate (IDI = 1.5%, NRI = 5.35%). Overall these results indicate an unlikely translation of IL-6 into clinical practice for this purpose. (C) 2014 Elsevier B.V. All rights reserved.