While neuropathological studies have established the pathology of dementia pugilistica to be similar to that of Alzheimer's disease, there is little information about the early histological changes caused by the repetitive trauma that eventually produces dementia pugilistica. We have examined the brains of four young men and a frontal lobectomy specimen from a fifth, age range 23-28 years, all of whom suffered mild chronic head injury. There were two boxers, a footballer, a mentally subnormal man with a long history of head banging, and an epileptic patient who repeatedly hit his head during seizures. The four autopsy cases were widely sampled; the lobectomy specimen was serially sliced after fixation. Routine stains were performed; inmmunostaining included beta-amyloid precursor protein, amyloid beta-protein (Abeta), tau and apolipoprotein E (apoE). Pathological findings in all five cases were of neocortical neurofibrillary tangles (NFTs) and neuropil threads, with groups of tangles consistently situated around blood vessels in the worst affected regions. No Abeta immunoreactivity was detected. The amount of neuronal apoE expression varied widely between the cases with no clear relation to the NFTs. The apoE genotype was determined in only two cases (both epsilon3/epsilon3). It appears that repetitive head injury in young adults is initially associated with neocortical NFT formation in the absence of Abeta deposition. The distribution of the tau pathology suggests that the pathogenesis of cytoskeletal abnormalities may involve damage to blood vessels or perivascular elements.