Methods developed for the qualitative simulation of dynamical systems have turned out to be powerful tools for studying genetic regulatory networks. A bottleneck in the application of these methods is the analysis of the simulation results. In this paper, we propose a combination of qualitative simulation and model-checking techniques to perform this task correctly and efficiently. By means of the example of the network controlling the initiation of sporulation in B. subtilis, we argue that this approach is well-adapted to the kind of questions biologists habitually ask and the kind of data available to answer these questions.