Using seven independent antibodies against the amino terminal to the carboxyl terminal sequence of tau, we biochemically analyzed and compared the neuropathogenesis of two Alzheimer's disease brains from the viewpoint of abnormal processing on tau, the major constituent of paired helical filaments. One showed typical Alzheimer's disease with senile plaques and intracellular neurofibrillary tangles. The other showed advanced Alzheimer's disease with senile plaques and virtually the sole of ghost tangles without intracellular neurofibrillary tangles. We confirmed the previous observation that the carboxyl thirds of tau are tightly associated with paired helical filaments isolated in the presence of SDS. We found that biochemically, ghost tangles were abnormally phosphorylated and lacked the final carboxyl terminal sequence as well as the amino half of tau, unlike intracellular tangles. From these biochemical results taken together with the current evidence for ubiquitin in ghost tangles, we concluded that ghost tangles were extensively processed and irreversibly transformed into highly insoluble extracellular deposits.