OBJECTIVE The aim of this longitudinal study was to test the hypothesis that CSF biomarkers in AD patients also may be forward-looking measures that are associated not only with the degree and profile of cognitive impairment but also with changes in cognition over time. METHODS Here, we assessed the association of CSF Abeta42, T-tau and P-tau with neuropsychological scores of disease severity, as well as the rate of disease progression, in 142 patients with Alzheimer's disease. All patients were part of a 3-year prospective longitudinal treatment study. RESULTS A more rapid progress in MMSE score reduction was seen in AD patients with T-tau levels higher than the upper quartile (800 ng/L) compared with Alzheimer's disease patients with lower T-tau levels (p = 0.008). We also found that individuals with T-tau > 800 ng/L performed worse in total scores and especially in memory and orientation when assessed with MMSE and ADAS cog than patients with T-tau <800 ng/L. Similar results were obtained for P-tau. No associations were seen between Abeta42 and cognitive scores or disease progression. CONCLUSIONS These findings support the hypothesis that increased levels of T-tau reflect the intensity of the disease and are associated with a more rapid disease progress.