EDMUS, the European Database for Multiple Sclerosis (MS), was established on the occasion of the first European Concerted Action for MS under the auspices of the European Community. The system is user-friendly and makes it possible to record and retrieve data relevant to MS. Within the framework of another European Concerted Action, several international multicenter trials are currently in progress. EVALUED, a validation of the EDMUS system, assesses the interrater variability; PRIMS examines the influence of pregnancy and the post-partum period on the course of MS; and PRESTIMUS investigates predictive factors in suspected MS. Further, planned studies include ERAZMUS (early azathioprine and interferon-beta treatment in MS) and AZASTOP, which is designed to evaluate the effect of stopping azathioprine treatment.