Inquiry, a prominent feature of the National Science Education Standards, is the instructional keystone that connects doing and learning science (NRC 2000). Because it is integral to the Standards, inquiry is also emphasized in science curriculum standards adopted at state and local levels. Inquiry-based classes allow for scientific learning through investigation, which develops the abilities students need to design and conduct scientific studies (NRC 2000). Project-based science (PBS) instruction addresses these criteria for inquiry. This article highlights ways to design and incorporate substantive PBS activities in the classroom.