We measured tau concentrations in cerebrospinal fluid (CSF) samples taken during the lifetime of 43 patients with Alzheimer's disease (AD) and correlated these values with neurofibrillary tangle (NFT) scores as well as glial fibrillary acidic protein (GFAP) expression as a marker of astrocytosis in the brain post-mortem. The CSF tau values showed a positive correlation with neocortical NFT scores (r = 0.44, p < 0.005), while GFAP immmunoreactivity did not correlate with CSF tau. This study reveals a high variation in CSF tau values in patients with neuropathologically confirmed AD (range 194-1539 pg/ml) and indicates that high CSF tau values in the late phase of Alzheimer's disease predict severe neurodegeneration as evidenced by increased NFT scores.