Research from the United States shows that gaps in early cognitive and noncognitive abilities appear early in the life cycle. Little is known about this important question for developing countries. This paper provides new evidence of sharp differences in cognitive development by socioeconomic status in early childhood for five Latin American countries. To help with comparability, the paper uses the same measure of receptive language ability for all five countries. It finds important differences in development in early childhood across countries, and steep socioeconomic gradients within every country. For the three countries where panel data to follow children over time exists, there are few substantive changes in scores once children enter school. These results are robust to different ways of defining socioeconomic status, to different ways of standardizing outcomes, and to selective non-response on the measure of cognitive development.