The purpose of this study was to develop and evaluate a diagnostically based curriculum for disadvantaged preschool children. For each of 3 years, 45 lower class Appalachian white 5-year-olds were equally divided into three groups. The experimental preschool group (EPS) received a structural curriculum designed to remedy specific, diagnosed deficits in language development, fine motor coordination, concept development, and socialization. Two contrast groups were used. The kindergarten contrast group (KC) received a traditional kindergarten program, while the "at home" contrast group (AHC) received only the pretesting and posttesting given to all groups. The experimental curriculum was annually revised to benefit from the past experiences. When the data from the populations of 3 years were combined, they revealed that in the intelligence category, the EPS mean was significantly greater than either the KC or AHC mean, and the KC mean was significantly greater than the AHC mean. Testing during the first grade, however, showed that the EPS and KC had stabilized in IQ by the end of their preschool year, but the AHC group gained enough in the first grade to cancel the IQ differences that formerly existed. Statistics for the other categories are also listed. (JS)