Frontotemporal dementia (FTD) is the third leading cause of dementia in large pathological series but tends to have an earlier age of onset than Alzheimer’s disease (AD) and Lewy body dementia, the most frequent and second most frequent forms of dementia. Semantic dementia (SD) includes impairment in the understanding of the meanings of words and difficulty in identifying objects. Semantic primary progressive aphasia, also known as SD, includes difficulties with naming and single-word comprehension although grammar and fluency are often spared. SD is a disorder that involves loss of semantic memory, anomia, receptive aphasia, and an actual loss of word meaning. The chapter presents some assessment tools that are those conducted by a psychologist or a neuropsychologist. Such an evaluation should include a clinical interview and neuropsychological examination. SD has been associated with ubiquitin-positive, TAR-DNA-binding protein-43 (TDP-43)-positive, tau-negative inclusions.