A large number of performance evaluation tools have been developed over the years to support the analyst in the difficult task of model building. As systems increase in complexity, the need is critical for tools that are able to help the user throughout the whole modeling cycle, from model building to model solution and experimentation. In this work we describe the main features of the TANGRAM-II modeling environment. The tool has a powerful and flexible model interface, unique algorithms for the numerical solution of models, includes an event driven and fluid simulators that provides a variety of facilities useful for obtaining the measures of interest, and has a traffic engineering environment integrated with the other tool modules.