Abstract
A stronger association has been found between multiple sclerosis and HLA-DR2 than -DQwl in south east Wales (prevalence c 113/10(5)) in contrast to recent observations in north east Scotland (prevalence 178/10(5). The complex relationship between the HLA system and multiple sclerosis, demonstrated in this and other studies, is explained more easily under a polygenic model of inheritance, in which environmental events and genes interact, than by the presence of a single susceptibility gene.