To compare assessments of malocclusion made by an orthodontist with the perceptions of children and their parents.A sample of 5,112 Malaysian schoolchildren was selected by a system of stratified random sampling based on state, ethnicity and gender. Each child was first allocated an IOTN (AC) grade by an orthodontist, after which the child and then the parents also recorded a grade. A smaller sub-sample of 720 children was also asked to identify the three worst AC pictures and to give reasons for their choice.The orthodontist scored 22.8% of the subjects in AC grades 8-10, 'Definite Need for Treatment' whilst only 5.8% of children and 4.8% of parents recorded these grades. If AC grade 6 is taken as the cut off point the proportions needing treatment would be 41.8%, 9.7% and 9.9% respectively. Similar proportions of boys and girls scored their own teeth in the 8-10 range but more girls than boys scored themselves in grades 1-3, 'No Need for Treatment'. Ethnic origin had no effect upon the perception of malocclusion by the children. Crowding, deep bite and tooth size were the three occlusal features that children liked least.The IOTN (AC) index appears robust in its reflection of the perception of malocclusion by children and parents respectively. Assessments were little affected by gender or ethnicity. However the scores of children and parents were much lower than those of an orthodontist trained in the use of IOTN.