This study examines how children learn information about the causes of illness (such as germs or cold weather) through conversations with their parents in two cultures. Mexican (Study 1, N = 35) and European-American (Study 2, N = 31) mothers and their children (ages 4 to 6) read picture books in which one of the characters either got sick or did not get sick with the common cold. Mexican dyads discussed health and illness in terms of maintaining a balance in the body. European-American families relied on germ-based explanations. In Study 3 (N = 429), parent’s beliefs about the cause of illness predicted their engagement in preventative behavior.