This paper describes GRAPE, an expert component for a scientific Conference Management System (CMS), to automatically assign reviewers to papers, one of the most difficult processes of conference management. In the current practice, this is typically done by a manual and time-consuming procedure, with a risk of bad quality results due to the many aspects and parameters to be taken into account, and on their interrelationships and (often contrasting) requirements. The proposed rule-based system was evaluated on real conference datasets obtaining good results when compared to the handmade ones, both in terms of quality of the assignments, and of reduction in execution time.