Currently there are no large-scale data on the prevalence of disordered eating behaviours in Irish children and adolescents. We examined the 2002 Health Behaviour in School Aged Children (HBSC) study to estimate those Irish children who are potentially at risk of developing an eating disorder. Body Mass Index (BMI) data, based on self-reported height and weight were available for 2,469 pupils (29% of all participants). This analysis showed that 32.2% of adolescents were underweight (BMI < 18.5 kg m(-2)) and 10.7% of this group 'thought they were too fat'. These latter (n-86) were identified as the 'risk' group and compared with group 2 (n = 717) who reported they were underweight and had indeed a low BMI and group 3, (n = 856) those with a normal range BMI (18.5-25Kg/m2). Those at risk were significantly more likely to choose a large silhouette, be unhappy, poorly satisfied with life and perceive themselves as not good looking, to have diet concerns, be bullied at least twice per month and feel they were average/below average in their academic work (all p < 0.001). These data indicate psycho-social associations with an important potentially pathological population sub-group of at risk children.