This plan for the longitudinal evaluation of a group of five different kinds of preschool programs involves a project conducted in a predominantly disadvantaged Australian community over the period 1975-79. Main project goals are (1) the determination of conditions under which particular preschool programs are most effective and (2) the evaluation of such programs. Involved are the development of four preschool programs and one home-based program, their implementation in the context of an Australian setting with a large proportion of disadvantaged children and the assessment of the various effects of these programs. The Mt. Druitt area near Sydney was chosen for its predominantly lower socio-economic status population with a large sub-population of preschool children. The five major types of programs represented emphasize, respectively: (1) behavior modification, (2) cognitive skills and structures, (3) competency orientation, (4) social and affective growth and (5) parent-child interactions in the one home-based program. Major comparisons to be conducted will be among the 5 program groups to determine initially the effects of different programs on specific groups of children. Subsequent comparisons will be made between the performance of those 5 groups during kindergarten and first grade and the performance of 4 comparison groups. Selection of measurement instruments is discussed, as well as statistical procedures to be used. (BF)