Research on children's concepts of health and illness has been dominated by two theoretical approaches. The first has been concerned with the delineation of age-related qualitative changes in children's concepts of health and illness and the interpretation of these changes within a Piagetian framework. The second approach, based on expectancy theory from social psychology, has focused on children's perceptions of vulnerability to health problems and the relationship of these to potential health behavior. Both approaches have emphasized children's concepts of illness or of health problems. Thus, there is a dearth of literature on concepts of health per se.