Literature related to eight major categories of variables affecting the experiences provided to children in preschools is reviewed in this paper. Categories initially discussed include contextual factors, characteristics of clients, characteristics of teachers and other assisting adults, and the preschool curriculum. A short discussion of the context of preschool education focuses on historical, philosophical, and cultural factors. Subsequently, attention is briefly given to age, socioeconomic status, and other variables, such as cultural differences between clients. Following discussion of interaction patterns of teachers and children, the review focuses on the preschool curriculum, providing examination of curriculum models, the immediate effects of preschool education, the long-term effects of different curricula, and lasting effects of preschool education in general. The remaining sections of the review provide background information and raise issues related to parent participation, program administration and sponsorship, program length, and environmental variables. Throughout the review a global perspective is maintained and research findings from several countries are reported. (RH)