The microtubule-associated protein tau plays a critical role in the pathogenesis of Alzheimer's disease (AD) and several related disorders collectively known as tauopathies. Development of tau pathology is associated with progressive neuronal loss and cognitive decline. In the brains of AD patients, tau pathology spreads following a predictable, anatomically defined progression pattern that can be followed by immunohistochemistry looking at brain post-mortem samples from Alzheimer patients at different stages of the disease. Furthermore, since it has been proposed that AD may be a synaptopathy and dendritic spines of pyramidal neurons are the major targets of cortical synapses, the analysis of dendritic spines is a useful tool to study the correlation between tau phosphorylation at specific sites, synaptopathy and cognitive impairment. Finally, characterization of phosphorylated tau in detergent-insoluble protein aggregates could also be an indication of the neuropathological staging in AD. Here, we describe these three complementary protocols to follow the development of tau pathology in Alzheimer's disease.