Children and adults often hold naive intuitive theories about how the physical world around them works, and their misconceptions can be difficult to change. Self-explanations have been found to be effective in producing better understanding of science (Chi, de Leeuw, Chiu, & LaVancher, 1994), and explaining another person's reasoning can also bring about cognitive change (Siegler, 1995). This study deals with one domain of physics-balance-and investigates the effects of 2 interventions on children who had either a procedure for balancing but could not explain it or had a naive theory. We pretested 140 children, ages 5 to 9 years, to assess their ability on a balance beam task and their knowledge about the principles of balance. These children were classified according to levels of representation derived from Karmiloff-Smith's (1992) Representational Redescription model. In this sample, 104 children could not explain the principles of balance or possessed a naive theory that all things had to balance in the center. These children were allocated to I of 2 intervention conditions. Approximately half of the children watched the experimenter model the correct solution to the balance task; the rest observed the model and were also encouraged to produce verbal explanations of what they saw. At posttest, a significantly higher number of children from the latter condition had improved their understanding of balance. The positive effects of interpersonal explanation are discussed in relation to Karmiloff-Smith's model of children's development, and the implications for teaching are highlighted.