Anaemia is a negative prognostic factor for patients with heart failure and impaired renal function, but its role in stroke patients is unknown. Furthermore, anaemia has been shown to influence the level of N-terminal pro-brain natriuretic peptide (NT-proBNP), but this is only investigated in patients with heart failure, not in stroke patients. Two-hundred-and-fifty consecutive, well-defined ischemic stroke patients were investigated. Mortality was recorded at 6 months follow-up. Anaemia was diagnosed in 37 patients (15%) in whom stroke severity was worse than in the non-anaemic group, whilst the prevalence of renal affection, smoking and heart failure was lower. At 6 months follow-up, 23 patients were dead, and anaemia had an odds ratio of 4.7 when adjusted for age, Scandinavian Stroke Scale and a combined variable of heart and/or renal failure and/or elevation of troponin T using logistic regression. The median NT-proBNP level in the anaemic group was significantly higher than in the non-anaemic group, and in a multivariate linear regression model, anaemia remained an independent predictor of NT-proBNP. Conclusively, anaemia was found to be a negative prognostic factor for ischemic stroke patients. Furthermore, anaemia influenced the NT-proBNP level in ischemic stroke patients, an important aspect when interpreting NT-proBNP in these patients.