Systems thinking inventory tasks have been developed to assess people's understanding of basic system concepts. Since 2000, these tasks have been used with different populations of students ranging from high school to MBA. The results have consistently shown that people have poor understanding of system concepts. This article focuses on the effects of an introductory system dynamics course on the performance with three of the systems thinking inventory tasks, i.e. department store, manufacturing, and CO2 zero emissions tasks. Students answered the questions before and after a course that takes 13 weeks. The performance in pre- and post-tests and the changes in performance, as well as the implications for further research, are discussed. Copyright © 2005 John Wiley & Sons, Ltd.