An expert system using computers was developed to change different health behaviors of elementary school children, and the system was evaluated in a pilot study that was designed to refine the system. Third- and fourth-grade children participated in Study 1 that was designed to demonstrate the processes of developing feedback messages. Eight health behaviors, including outdoor play, sleep, and TV game control were analyzed by using this system. Behavioral elements such as gender, stages of change, facilitators, barriers, costs and benefits of each behavior were used to develop messages based on previous research. Finally, 6 school nurses and 11 children confirmed the expressions and the nuances of the messages to adjust for gender, the stage of change and age groups of each behavior. Then, these messages were incorporated into the system software. In Study 2, children (N=97) evaluated their stage of change in each behavior and received message sheets through the expert system. The results indicated high evaluation scores for careful reading, understanding, attention, novelty, and adjustment. [ABSTRACT FROM AUTHOR]