The vast majority of Down’s babies have varying degrees of intellectual developmental deficits, and very few are bright. The main features of Down syndrome are intellectual backwardness, peculiar facial features and growth retardation, and may be associated with a variety of malformations. The severity of clinical manifestations varies with the percentage of abnormal cell karyotypes. The most prominent and severe clinical manifestation of Down syndrome is mental retardation. The majority of children with Down’s syndrome have varying degrees of mental retardation, which becomes more pronounced with age. There is no effective treatment for this disease. Comprehensive measures are needed, including medical and social services, long-term patient education and training for patients to acquire certain job skills. Infections should be prevented in Down’s babies, and surgical correction may be considered if accompanied by congenital heart disease, gastrointestinal or other malformations.