This article analyzes children's ideas of health using a Piagetian developmental framework and draws implications for health education. Young children see health as a positive, enabling concept unassociated with illness. Older children associate health and illness but see health as long term and sickness as short term. The development of a concept of health follows a progression similar to that outlined by Piaget and verified by researchers looking at related concepts. An understanding of cause and effect, the ability to conserve ideas and reverse thinking, consider the future and formulate at least tentative hypotheses are processes which mature with age and experience. The concept of health expands and changes as these processes mature. This analysis suggests that health oriented educational programs which are consistent with the child's ability to process information might be more effective than traditional disease-oriented programs. It also raises several questions for future research.