Data on two preschool intervention programs for children from low-income families are discussed. The first program, the Karnes Preschool Program for the amelioration of learning deficits, is characterized by a structured format based on psychological theories. Its curriculum is designed to develop the basic language processes and to teach content in mathematics, language arts, social studies, and science. The other program, the Traditional program, aims to advance the personal, social, motor, and general language development of the children. Data were collected on 60 four-year-old children who were assigned to one of four classes, of 15 each, on a stratified basis such that the sex, race, IQ, and ages of the children in the classrooms were comparable. Results include: (1) Initially, the Karnes program more effectively promoted cognitive development than the Traditional program; (2) After three years, the differential program effects of the two programs were no longer statistically evident; and (3) the Cognitive functioning of the children at the end of a five-year period was significantly above their initial level. It is concluded that the Karnes Program significantly enhances the functioning of children in the cognitive, social, and probably affective areas. It is recommended that serious consideration be given to the further study and implementation of structured programs. (Author/CK)