We aimed to find out the number of patients with osteoradionecrosis (ORN) being treated by hyperbaric chambers in the UK during 2006-07, and the protocols that were being used. We did a telephone survey of 76 chambers to find out whether they treated patients with ORN, how many patients they treated in 2006-07, what chamber pressure they used, the duration of each session, and the total number of sessions/patient. A total of 25 chambers treated 273 patients with ORN in 2006-07; 10 were listed by the British Hyperbaric Association (BHA) and 15 were at multiple sclerosis (MS) centres. MS centres treated 23 (8%) of patients with ORN with a variable number of sessions of shorter duration and lower pressures than the chambers listed by the BHA. Most BHA chambers treated patients at 2.2 ATA for 90 min/session with 30 preoperative and 10 postoperative sessions/patient.