The unique sensitivity of magnetic resonance imaging (MRI) in detecting disease activity in multiple sclerosis (MS) and the objective nature of the information obtained suggest that MRI will be a useful and reliable way of monitoring treatment trials. There is a need to develop an appropriate database which would provide a standardised means of assessment, not only of MRI, but also of essential clinical information. As part of the program of Concerted Action in Multiple Sclerosis, funded by the Commission of the European Community (CEC), we have developed a database for recording serial brain MRI results. The database consists of core, entry and follow-up sections. Both entry and follow-up parts are subdivided into clinical, MR system and MRI data. We expect that the use of this database will maximise efficiency of MRI monitoring in MS treatment trials, particularly in multicentre studies.