Frontotemporal dementia (FTD) is a form of degenerative dementia that commonly affects younger people. It typically presents as radical alterations in a person’s behaviour, reasoning, and judgement. Yet, there is wide variation both in clinical characteristics (demographics, behavioural, cognitive, and neurological) and in the underlying neurobiology (pathology and genetics). Importantly, in recent decades, the relationship has been highlighted between the behavioural disorder of FTD (bvFTD) and progressive disorders of language and conceptual knowledge that come under the rubric of primary progressive aphasia. This webinar is designed to provide an overview of the current state of knowledge about FTD, with a focus on sources of heterogeneity. In the talk I explore differences in demographic features, such as onset age and length of survival. I describe variations in the pattern of behavioural change and the nature of language and semantic disorder, with specific clinical examples. I consider performance on executive tests and its qualitative characteristics. I summarise different associated neurological signs, the distinct pathological types and the most common genetic mutations. I consider the predictive inter-relationships between clinical characteristics and underlying neurobiology and discuss their relevance for clinical diagnosis and management.