The number of patients in buprenorphine opioid substitution therapy (BOST) or methadone opioid substitution therapy (MOST) programs is increasing. If these patients require surgery, it is generally agreed that methadone should be continued perioperatively. While some also recommend that buprenorphine is continued, concerns that it may limit the analgesic effectiveness of full mu-opioid agonists have led others to suggest that it should cease before surgery. However, no good evidence exists for either course of action. Therefore, we undertook a retrospective cohort study comparing pain relief and opioid requirements in the first 24 hours after surgery in 22 BOST and 29 MOST patients prescribed patient-controlled analgesia. There were no significant differences in pain scores (rest and movement), incidence of nausea or vomiting requiring treatment, or sedation between the BOST and MOST patient groups overall, or between those patients within each of these groups who had and had not received their methadone or buprenorphine the day after surgery. There were also no significant differences in patient-controlled analgesia requirements between BOST and MOST patient groups overall, or between patients who did or did not receive MOST on the day after surgery. BOST patients who were not given their usual buprenorphine the day after surgery used significantly more patient-controlled analgesia opioid (P=0.02) compared with those who had received their dose. These results confirm that continuation of buprenorphine perioperatively is appropriate.