This is the final report of the Ancona Montessori Research Project for Culturally Disadvantaged Children begun in 1965 to investigate the effects of a modified Montessori program for disadvantaged children in the preschool and early elementary years. This report deals with the academic year 1969-1970, in which 29 disadvantaged children and a comparable group of 29 middle class children are the central focus of study. In addition, there is a followup on the school careers of disadvantaged children who attended Ancona at one time. A number of hypotheses about the potential effects of the project on the children's cognitive, social development are studied. Part I of the report deals with findings relative to the nursery school children, and includes a discussion of data from three measures of intellectual development (Stanford Binet, WPPSI and Merrill-Palmer) and from tester and teacher ratings of school-related behaviors and attitudes and social interaction. Part II details findings on the elementary school children and followup data on children who attended Ancona in previous years but are now elementary school students in other schools. In addition, data regarding children whose families have had long term involvement in the school is discussed. The appendix includes Ancona school Head Start program ratings of behavior during individual intelligence testing. (MS)