We analysed different subsets of lymphocytes from peripheral blood (PB) and cerebrospinal fluid (CSF) by flow cytometry in order to determinate alterations in patients with multiple sclerosis (MS) in acute relapse and viral inflammatory neurological disease (IND). We found increased levels of adhesion molecules (LFA-1 and beta1 integrin) in the CSF of patients with MS and IND compared to NIND. CD4+/CD8+ ratio was significantly higher in CSF of MS as compared with all groups analysed and compared with PB. We detected a significantly higher expression of the interleukin-2 receptor in PB of MS patients when compared with other groups. In patients with IND a significant higher expression of the interleukin-2 receptor was found in the CSF compared with MS and NIND. Our findings indicate that the activation of T lymphocytes primarily occurs in the peripheral immune compartment in MS and the increase of adhesion molecules in CSF is related to inflammatory disorders and not only to MS.