Graphing predictions is especially important in classes where relationships between variables need to be explored and derived. In this article, the author describes how his students sketch the graphs of their predictions before they begin their investigations on two laboratory activities: Distance Versus Time Cart Race Lab and Resistance; and Ohm's Law Lab. Prior to collecting data, graphing a prediction helps students evaluate the relationship between their variables and establishes the foundation for the scientific concepts and mathematic principles underlying the investigation. After collecting and graphing data, it is easier for students to determine if they supported or rejected their prediction if they have a graph of their prediction in front of them. Perhaps most importantly, graphing their predictions forces students to analyze their thinking process prior to gathering data. It also provides a theoretical context for both the mathematic principles and scientific concepts underlying their investigation. This process leads students to a better understanding of both the nature of science and the nature of mathematics. (Contains 5 figures.)