The Norwegian Government has decided to reform the care of the mentally retarded by placing the responsibility for medical and social care with the local authorities. From 1 January 1991 the mentally retarded are to be integrated into the community. Persons with Down syndrome constitute 20-30% of the mentally retarded in institutions. The syndrome is the most common single cause of mental retardation. It represent both a medical challenge and a challenge in regard to home support, work, leisure activities and habilitation. Habilitation means identifying the fundamental deficiencies, incorporating this knowledge into plans for treatment and evaluating progress in social functioning and individual capacity. This presentation emphasizes clinically important information about the syndrome and medical complications both in the early stage of life, and among youths and adults in particular. Owing to difficulties in communication, there are often diagnostic problems. However, when recognized, many of the complications can be treated effectively.