A longitudinal research study of the growth and development of 10 severely mentally handicapped mongoloid (Down's Syndrome) children reared together in a state hospital was conducted. They were tested regularly on the same scales, providing comprehensive histories of mental, psychomotor, and physical growth. When comparison with similar children reared at home emphasized the declining developmental patterns of the institutionalized group, an environmental stimulation program (eventually including reading) was designed to overcome their relative retardation. Intensive language stimulation training was the focal point. Described are means used to make the environment more stimulating, better structure daily routine, and motivate staff. Initial language stimulation and articulation training is outlined, including modifications made as the program progressed. Aspects of reading training and instruction are summarized. Findings thus far show improvement in articulation, greater expressive use of language, more extensive receptive language, significant increase in intellectual ability, and ability to read and enjoy simple books. Asocial behaviors have almost disappeared and destructive, random, or stereotyped acts have decreased. (KW)