Cerebrospinal fluid (CSF) levels of interleukin (IL)-6, IL-11 and leukaemia inhibitory factor (LIF) were evaluated in 43 patients with Alzheimer's disease (AD) and 24 patients with frontotemporal lobar degeneration (FTLD) as compared with 30 agematched controls (CON), and correlated with clinical and demographic data and with CSF biomarkers amyloid beta (A beta)42, total tau and tau phosphorylated at position 181 (P-tau). CSF IL-11 mean levels were significantly increased in AD and FTLD as compared with CON (6.5 +/- 4.6 and 6.6 +/- 5.1 versus 3.1 +/- 3.3 pg/ml, P = 0.009). IL-6 mean levels did not differ between patients and CON (P > 0.05),whereas LIF levels were not detectable in patients or in CON. In AD patients, a significantly positive correlation between MMSE scores and IL-11 CSF concentration was observed (r = 0.344, P = 0.028). No correlations with CSF A beta 42, total tau and P-tau were found. IL-11, but not IL-6 levels are increased in AD and FTLD, and the highest peaks were observed in patients with a less severe degree of cognitive deterioration, therefore suggesting a role of this cytokine in early phases of neurodegeneration.