The British Neurological Surveillance Unit was set up in January 1993 with the aim of co-ordinating and improving the ascertainment of rare neurological disorders in the United Kingdom by using a system of nation-wide active surveillance. The unit provides a service for individual investigators who must first submit possible studies to a scientific advisory committee. Once accepted the condition is listed on a report card which is sent to every member of the British neurological community every month. The cards are easy to use, and all the reporting neurologist has to do is tick a box indicating whether a case has (or has not been) seen. At the end of every month the individual investigators then initiate further follow-up by contacting the reporting neurologists. In the first year of operation the scheme has assisted in the surveillance of 6 disorders and the following number of verified cases have so far been ascertained: polio in adults (n = 0); acute psychological disorders in patients with epilepsy (n = 75); Guillain-Barré syndrome in the south of England (n = 32); epilepsia partialis continua (n = 40); amyloid neuropathy (n = 12), and agenesis of the corpus callosum (n = 24). The monthly response rates are between 65 and 75%, with the eventual aim of achieving over 90% after the scheme has become more established.