This Cooperative Language Development Project had two objectives: (1) to provide a modified language program for culturally disadvantaged first graders and (2) to evaluate the effectiveness of the program in terms of academic, intellectual, and linguistic growth. In a 2-year intervention program experimental versions of the Peabody Language Development Kit (PLDK) and the Early-to-Read Initial Teaching Alphabet (ITA) were used for an experimental group. There were 630 subjects the first year and 343 the second year. A conventional basal reading program with no language stimulation was used for a control group with 102 subjects the first year and 41 the second year. The combination of ITA and 2 years of PLDK produced the most effective results. Reading achievement after 2 years was equal for both groups. The effects of PLDK on intellectual functioning are questionable. These findings must be viewed cautiously since (1) increments favoring the ITA and PLDK may not last through the third grade, and (2) present research does not suggest the same superiority of ITA as demonstrated in this project. However, ITA and PLDK hold promise for inner-city slum children with reduced verbal ability, restricted and nonstandard English, and inability to articulate speech sounds clearly. (DO)