The Effective Pre-school Provision in Northern Ireland (EPPNI) project investigated the effects of pre-school education and care on children's development for children aged 3-8 years old. The EPPNI team collected a wide range of information on over 800 children who were studied longitudinally until the end of Key Stage 1. Data were collected on children's developmental profiles (at ages 3, 4, 5, 6, 7, and 8 years), background characteristics related to their parents, the child's home learning environment, and the pre-school settings children attended. Eighty pre-school settings were drawn from a range of providers (nursery schools/classes, playgroups, private day nurseries, reception classes and reception groups). A sample of 'home' children, (who had no or minimal pre-school experience) were recruited to the study at entry to school for comparison with the pre-school group. In addition to investigating the effects of pre-school provision on child outcomes, EPPNI included three intensive case studies of pre-school settings. This research report summarises the empirical work published in thirteen Technical Papers (See Appendix 3). Those interested in methods or detailed findings should consult the Technical Papers because only the main findings and implications appear in this report.