A simulation framework is presented (WISS, Wageningen Integrated Systems Simulator) which targets the agro-ecological modelling domain. Especially simulation for a large number of locations, such as in detailed regional and global simulation studies. The framework strengths are in modularization, control, speed, robustness and computational protection (multiple system checks during simulation). The WOFOST model is currently implemented in WISS, through which it is used in a number of Wageningen University and Research projects. WISS is written in Java and the framework code is freely available.