The notion that cervical lymphatic surgery may influence the development of multiple sclerosis has been suggested before. Recent work in experimental allergic encephalomyelitis lends further support to this idea. We, therefore conducted a case:control study of tonsillectomy in multiple sclerosis. We found no evidence to suggest that tonsillectomy affects susceptibility to multiple sclerosis. This result supports previous studies, which have largely failed to show any link between prior tonsillectomy and the subsequent development of multiple sclerosis. In addition, we failed to show any effect of tonsillectomy on the extent of cerebral demyelination as assessed clinically or with magnetic resonance imaging.