Background: Self-injurious behaviour is a chronic condition among people with intellectual and developmental disabilities for which there is no known cure. The pain hypothesis suggests that individuals who engage in self-injury have altered or diminished pain perception. The purpose of the present study was to assess how frequently individuals diagnosed with an intellectual and developmental disability who engage in chronic self-injury displayed non-verbal signs of pain in relation to their self-injury. Methods: We videotaped four participants (aged 28-50 years) in their homes during times when they were likely to engage in self-injury. Using continuous recording measures, we coded videotapes for the frequency and duration of self-injury and expressions of non-verbal pain-related behaviours. Sequential analyses were conducted to identify temporal relations between pain-related behaviours and self-injury. Results: Our data suggest that the existing measures of pain may be systematically related to instances of self-injury. The relationships, however, appear to vary depending on the person who engages in self-injury, the environmental contexts in which the self-injury occurs, and perhaps, the type of self-injury in which the person engages. Conclusions: These results support some of the findings of Symons "et al." and they raise questions about the blunted nociception hypothesis of self-injury.