We report dynamic data on the spatial pattern of sapling recruitment over a three-year interval in a 50 ha<latex>$\dagger $</latex> mapped plot Barro Colorado Island (BCI), Panama. We analysed sapling recruitment of a given tree species against recruitment of all other competing tree species, as a function of distance to nearest conspecific adult tree. Strong negative conspecific effects of large trees on saplings were detectable in a few very common species, but not in many others. The power to detect conspecific effects was evaluated in model tree populations in which the strength of these effects was known a priori. The measured conspecific effects appear strong enough in the densest species to prevent them from assuming complete dominance. However, many species do not show these effects, and we conclude that these effects play only a limited contributing role to the maintenance of tree species diversity in the BCI forest.