The article begins with a critical look at the existing literature explaining self-injury by people with significant learning disabilities and self-harm by those with mental health difficulties. It suggests that the different conceptualizations are perhaps less distinct than might initially appear, and that behavioural similarities between those with and those without learning disabilities might be greater than previously believed. The notion of "career" is presented as a means of explaining the process by which people with learning disabilities engage in self-injury and subsequently integrate it into their lives. Data are subsequently presented from a number of life histories of people with learning disabilities to illustrate the development of self-injury over the life course. The findings of the research indicate that the development and consolidation of self-injury over time conforms to the expectations of a career and provides reason to question the contemporary separate categorization of the behaviour of people with significant learning disabilities. The evidence suggests that the relationship between self-injury and learning disability is best explicable in terms of its intelligibility, rational behaviour in the context of the individual's life.