Design A randomised controlled trial in an NHS hospital orthodontic clinic. Intervention Participants either received an appointment or an appointment plus a reminder at least 2 weeks before their appointment. The reminder letter was sent with a stamped addressed postcard, which the patient was asked to return, to confirm the appointment. Outcome measure Patient attendance at the clinic. Results A total of 231 patients were entered into the study. Patients who received a reminder and returned the confirmation were significantly less likely to fail the appointment than those who did not receive a reminder (see Table 1). 27% of girls failed appointments compared with 15% of boys. Those from areas of high social deprivation were more likely to fail to attend appointment than people who were more affluent. Conclusions The use of postal reminders for orthodontic consultation appointments appears to result in a useful increase of appointments that are kept or cancelled in advance but does not counteract the effect of social deprivation on attendance.