In vivo studies have been encouraging, with significant binding demonstrated in frontotemporal dementia due to mutations in the MAPT) gene10 12 32 and in progressive supranuclear palsy.13 This contrasts with reports from postmortem studies, which predominantly describe low level binding to the tau aggregates of frontotemporal lobar degeneration.14 33 34 These postmortem studies make it increasingly clear that the primary, tertiary and quaternary structures of tau, as well as the type and maturity of tau pathology,34 are important determinants of [18F]AV-1451 binding. Here, MAPT is linked to Classical progressive supranuclear palsy.