This review summarizes the clinical, imaging, and pathological features of frontotemporal dementia (FTD). Clinicians have become increasingly sensitive to FTD in the differential diagnosis of Alzheimer's disease. Clinical subgroups of FTD patients have been recognized, including patients with progressive non-fluent aphasia, semantic dementia, and behavioral disorder with executive difficulty. The clinical, neuroimaging and neuropathological profiles associated with these clinically defined subgroups are examined.