SUMMARY. This article makes the case for an engineering knowledge community. We begin by discussing the differences between science and technology. We next discuss the similarities and differences between engineers and scientists. Next, we analyze previous research into the information use behaviors of engineers. Finally, using the research results from the NASA/DoD Aerospace Knowledge Diffusion Research Project, we compare and contrast aerospace engineers and scientists as a means of developing similarities and differences between engineers and scientists in terms of their information-seeking behavior. The goal of this article is to demonstrate that engineers are not scientists and that knowledge production and use differ in engineering and science. We believe that the current model used to explain information-seeking behavior assumes no difference between the information-seeking of engineers and scientists. The distinctions between engineering and science, engineers and scientists and the information-seeking behaviors of engineers and scientists have multiple implications for providing information services, knowledge management, and diffusing knowledge. The message to libraries is "know thy customer."