Studies suggest that sedentary lifestyles are increasing with the average adult spending 50–60% of the day sitting. This change in lifestyle activities poses a risk not just to a person’s general health but also for the development of a pressure ulcer, particularly in people who are forced to sit for extended periods of time due to illness or disability. The purpose of this article is to define and categorise pressure ulcers. To explore how and where pressure ulcers develop in the seated individual, the risk factors from direct and indirect forces when seated and the evidence base to explain why pressure ulcers develop when sitting.