The rapid expansion in early childhood development programmes throughout the world in the last two decades attests to the growing recognition that preschool intervention programmes have the potential to contribute significantly to the enhancement of children's development and capacity for learning from their earliest years. Research continues to expand this knowledge base, and international studies confirm that good preschool programmes improve children's health and nutrition status as well as their mental and psychosocial development. Two findings with far-reaching implications are that children from low-income families derive greater benefits from early intervention programmes than their better-off peers, and that high quality programmes produce positive long-term effects on development throughout adulthood (Rutter 1981; Zigler and Gordon 1982; Clarke-Stewart and Fein 1983; Berrutta-Clement et al. 1984; McGuire and Austin 1987; Myers 1992; Weikart 1992).