The purpose of this study was to describe the development of elementary students' skill in making predictions and of their understanding of what predicting means. The study involved observing and assessing the performance of 167 children on the Physical Manipulation Test (PMT), a test involving the manipulation of science materials and equipment. Children were interviewed about what they understand predicting to mean, how they use it at school and at home, and why they think it is important. For each of the seven topics tested, even the youngest children were able to offer predictions. Accuracy varied with the topic, increasing between Grades 1 and 4 and leveling off after that. The increase in skill involved children's growing ability to attend to patterns discerned through their own observations. Four levels in the development of predicting skill, as it relates to particular topics, are described. Children's understanding of predicting showed steady improvement through Grade 6. Children's awareness of their use of predicting at school and at home, and their ability to explain the importance of predicting, also increased through Grades 1 to 6, with a spurt at Grade 4. Children understood predicting to be an internal process in which one uses knowledge to anticipate a future event; they regarded predicting as an important way of being intellectually involved with the world.