A growing body of evidence suggests the involvement of inflammatory mediators, including cytokines, in the development of ischaemic brain lesions. The aim of the present study was to investigate whether tumour necrosis factor-alpha (TNF-alpha), the proinflammatory cytokine, contributes to early pathophysiological mechanisms leading to brain damage as a consequence of acute stroke. We have studied TNF-alpha levels in cerebrospinal fluid (CSF) and serum in 23 stroke patients within the first 24 hours after ischaemic stroke, confirmed by computerized tomography of the brain (CT). The control group consisted of 15 patients with the diagnosis of tension headache and neurasthenia. In stroke patients the levels of TNF-alpha both in CSF and serum were significantly higher in comparison with the control group. The positive correlation between the levels of TNF-alpha in CSF and serum of the studied patients has been observed. Furthermore, a positive correlation between both TNF-alpha levels in CSF and serum and the volume of evolving brain infarct have been shown.