This paper analyses the occurrence and causes of reduced mental ability and its handicapping consequences with the objective of highlighting those areas where there is most opportunity for either preventing its incidence or alleviating the distress it generates. And it describes efforts made to improve services for the comparatively small number of more severely handicapped individual since the publication of the 1971 White Paper Better Services for the Mentally Handicapped (HMSO 1971)- In discussing the inter-related pattern of NHS and local authority care which has emerged it also considers the likely impact of economic restraints and new thinking on the social and educational needs of mentally handicapped people on official targets for service development up to the early 1990s.