Problem statement: In the teaching of graph theory algorithms it is im portant that students can experiment them on numerical instances in order to fully understand their logical meaning and to learn how they can be implemented. Approach: We developed an open source Java framework to help students in their approach to the study of graph al gorithms. The framework was implemented so as to be portable and easy to use. In addition, we includ ed a library that anyone can easily use to develop custom algorithms. Results: The framework, which is currently in use at the Uni versity of Bologna, and is available on-line, presently includes four b asic algorithms in graph theory, for the solution t he following problems: shortest spanning tree, shortes t paths, maximum flow, and critical path. It includ es an intuitive graphical user interface, and gives th e users the possibility of performing a "step-by-st ep" execution. Conclusions: The presented Java framework constitutes a first st ep towards the implementation of didactical instruments for the teaching of graph theory. Future developments will also include a new major release and an implementat ion targeting the Microsoft. NET framework.