This paper discusses the creation of interactive computer simulations that implement virtual laboratories in the field of Control Engineering education. Easy Java Simulations (Ejs, http://fem.um.es/Ejs/), a Java-based tool that helps create interactive dynamic simulations, is introduced. This tool can be used on its own, generating standalone Java applications or applets, or in conjunction with Matlab/Simulink, using them as the internal engine that describes and solves the model. We describe in this paper this particular feature in detail, and provide some examples that show the advantages that this tool offers to the world-wide engineering education community. Ejs is a freeware, open source, tool aimed for educators with low profile in programming but deep knowledge on certain technical and scientific fields. The tool allows to develop complete, interactive simulations in three steps: describing the mathematical model (optionally using Matlab/Simulink), building the user interface using off-the-shelf graphical elements, and connecting certain properties of these elements to the variables of the model. This last step is the key point to transform a classical simulation into a full interactive application. ß2005 Wiley Periodicals, Inc. Comput Appl Eng Educ 13: 84À98, 2005