Background: Using mechanical restraints to protect a person who engaged in dangerous self-injury was decreased by manipulation of an establishing operation involving the client choosing the staff person who would work with her. Materials and Methods: The client was a 28-year-old woman diagnosed with autism, bipolar disorder, static cerebral encephalopathy, moderate intellectual disabilities, hypotonia and musculoskeletal deformities. She had a history of biting herself and further bites could produce irreversible nerve damage. Mechanical restraints were applied when she bit, tried to bite herself or asked for them. Results: When she was allowed to choose staff members, the use of mechanical restraint decreased. Conclusion: Reducing the time spent in mechanical restraint by giving the client a choice of staff members who would work with her demonstrates that such a choice may be an establishing operation. The usefulness of cumulative records and scatterplots to evaluate changes in the occurrence of self-injurious behaviour (SIB) and associated mechanical restraint is shown as are the advantages of using alternating treatment designs to assess the effectiveness of treatment conditions for someone who exhibits long-term cyclic behaviour.