This article presents a review of the literature on object permanence with an emphasis on research on children with severe disabilities. Object permanence is the realisation that objects continue to exist in time and place even when they are no longer visible. This understanding is achieved across Stages IV-VI of Piaget's Sensorimotor Period. Children with intellectual disability, physical disabilities, blindness, and autism develop object permanence in a similar sequence although at a slower rate than children without disabilities. Challenges with regulation make it difficult for children with autism to demonstrate object permanence knowledge in Stage VI tasks. There is ample evidence that children with severe disabilities benefit from direct and systematic instruction of object permanence. Assessment-based instruction, establishment of visual attention, consideration of the characteristics of the object to be hidden (including the impact on differential attention), repeated naming of the object, individually appropriate prompting procedures, and direct reinforcement have been found to support mastery of object permanence in children with disabilities.