<i>Background</i> - Health registries may yield important data for epidemiological studies. However, in order to be a valuable source for information, the registered data have to be correct.<p><p> <i>Objectives</i> - The aim of the study was to validate data from the Norwegian Patient Registry (NPR) regarding multiple sclerosis (MS).<p><p> <i>Materials and Methods</i> - We obtained data ...