This paper reports the results of a study of the reliability of a modified version of the Index of Orthodontic Treatment Need (IOTN) for use in oral health surveys. Twelve non-specialist dental examiners were trained in the use of the Modified IOTN using a standardised teaching protocol lasting approximately 1.5 hours. Following a school-based calibration exercise it was found that nearly all the examiners achieved either good or excellent agreement (mean Kappa=0.74). The average sensitivity and specificity scores were 0.90 and 0.84, respectively. The Modified IOTN appears to overcome the training and reliability problems that often accompany the use of orthodontic indices by non-specialists in oral health surveys.