Behavioural experiments are a core component of cognitive therapy for PTSD (CT-PTSD). When well designed and implemented, they are a powerful way to help clients evaluate and modify beliefs about the trauma and its consequences. They can support and enhance in-vivo tasks, promote alternative coping strategies, and provide new information with which to update memories. Importantly, behavioural experiments can be integral to overcoming common obstacles in PTSD treatment. This skills class will begin with an overview of the “off the shelf” behavioural experiments commonly used in PTSD treatment, focusing on each element of a typical cognitive formulation. Building on this, and using case vignettes, clinical material and video excerpts, participants will learn how to collaboratively implement experiments that are creative, conceptually rigorous, and highly personalised. This will include experiments conducted in and out of the office, using technology, as homework, and when returning to the scene of the trauma. The workshop will also discuss how to use experiments both in a planned and spontaneous way to support other elements of CT-PTSD.