OBJECTIVE To test the effectiveness of different systems of reminding patients about their appointments in order to reduce the rate of failed attendance. The expense in implementing a reminder system for patients was also estimated. METHODS A clinical study in a single-handed dental practice. METHODS Patients were reminded about their appointment using either postal, manual telephone or automated telephone reminders (or all three combined). A control group received no reminders. 500 patient attendances were recorded in each group. RESULTS Patients failed to attend for 130 of the 2500 appointments considered in the study. There was a significant reduction in the failed attendance rate from 9.4% (with no reminder) to a minimum of 3% when a reminder was given to the patient before the appointment. However, there was no significant difference among the four reminder test groups, indicating that the form of the reminder made no difference to the failure rate. CONCLUSIONS Reminding patients using postal or manual telephone techniques is effective at improving attendance. All of the reminder methods, telephone and postal, provided net cost savings rather than additional costs.