The Cross Grid project will develop , implement and exploit new Grid components for interactive compute and data intensive application like simulation and visualisation for surgical procedures, flooding crisis team decision support systems, distributed data analysis in high-energy physics, air pollution combined with weather forecasting. The elaborated methodology, generic application architecture, programming environment, and new Grid services will be validated and tested thoroughly on the CrossGrid testbed, with an emphasis on a user friendly environment. The work will be done in close collaboration with the Grid Forum and the DataGrid project to profit from their results and experience, and to obtain full interoperability. This will result in the further extension of the Grid across eleven European countries. .