Early childhood development is recognized as a global priority, but questions remain regarding how to best serve the needs of disadvantaged children in low- and middle-income countries. We study the effects of a high-quality center-based early childhood intervention on the development of disadvantaged children in Colombia. We conduct a randomized controlled trial with over 1000 children followed longitudinally over a five-year period. The intervention leads to positive and sustained effects on children’s health, and positive effects on cognitive development that dissipate in the last year of the program. We find no effect on socio-emotional development or on the home environment.