Seedling demography data are provided in annual censuses of 600 seedling plots in an equatorial, ever-wet rainforest in eastern Ecuador, in Yasuní National Park. This long-term study uses standardized methodology from the Smithsonian ForestGEO network of plots, and in particular coordination with similar studies in Luquillo, Puerto Rico, and Barro Colorado Island, Panama. We address hypotheses about the maintenance of forest diversity and long-term variation, and link our data to companion studies of flowering and fruiting phenology and sapling and adult dynamics in the Yasuní Forest Dynamics 50-ha Plot. The project is ongoing, and additional data will be added as they are processed.