This research review focuses on the effects of early intervention on the preschool children of low-income families, examining studies of intervention programs begun in the 1960s through the present. It then relates this analysis to the new Georgia Prekindergarten Program. The interventions reviewed are grouped into four hierarchical categories based on their relationship to the children's: (1) microsystem, or immediate environment; (2) mesosystem, or connections among children's immediate settings, such as home and school; (3) exosystem, including the social settings that affect but do not contain the child, such as community agencies; and (4) macrosystem, or broad culture. The review concludes that many interventions undertaken since the 1960s have failed to address all four of these settings, and thus have had mixed success. By contrast, the review notes, the Georgia Prekindergarten Program is designed to provide a comprehensive program to intervene at all four levels of disadvantaged preschool children's environment. Contains 91 references. (MDM)