The course of frontotemporal dementia (FTD) is examined in a prospective, incipient clinical cohort. Three hundred nineteen patients were followed yearly for an average of 3.6 years. The relative frequencies at presentation were Behavioral variety (FTD-bv) 37.6%, Primary Progressive Aphasia (PPA) 31.6%, possible PPA 10.6%, Corticobasal Syndrome (CBDS) and Progressive Supranuclear Palsy (PSP) 8.1%, Semantic Dementia (SD) 6.6%, and possible FTD 5.3%. The age of onset was significantly lower in the FTD-bv and SD groups than in the rest, but survival and sex distribution was similar in all groups. The evolution is characterized by the appearance of additional FTD syndromes in two-thirds of the patients. A significant association of SD with FTD-bv and CBDS/PSP with PPA was found. The Frontal Behavioral Inventory was highly sensitive and specific for FTD-bv. Visuospatial function was preserved except in CBDS/PSP. The clinical diagnosis showed a positive predictive value of 87% against autopsy in 67 patients. Multiple syndromes increase the likelihood of FTD pathology. In conclusion, the clinical associations follow the tau-negative and tau-positive pathologic dichotomy to some extent, but there is too much overlap to consider the clinical groups or their associations separate diseases.