To gain further knowledge about rare genetic diseases, a world wide method for data collection via the Internet has been established. This new approach will improve collecting valuable data from single case reports. RAMEDIS saves standardised patient data which will be usable for statistics, longitudinal examinations and co-operative studies in future time. Embedded in the scene of the German Human Genome Project, RAMEDIS directly will enable phenotype-genotype correlation's. Technically RAMEDIS is based on the Oracle database management system with some additional tools. Since November 2000 first case reports are committed online. Beside the better characterisation of clinical heterogeneity of rare diseases, there may be a great benefit for the treatment of these patients in whom prospective studies are otherwise expensive and difficult to perform. Quality of clinical diagnostic process and therapy will increase.