Treefall gaps are through to contribute to the diversity of plants in tropical forests by providing opportunities for niche differentiation in modes of regeneration. To examine this hypothesis, we studied the survival, diameter growth, and recruitment of saplings in ≥100 species of woody plants in a 50—ha permanent plot of moist tropical forest on Barro Colorado Island, Panama, from 1982 to 1985. The performance of saplings in low—canopy sites (10 saplings/ha) species appeared to be generalists. Many rare (<1 sapling/ha) or occasional (1—10 saplings/ha) species survived significantly (P ≤ .05) less well than the average survivorship of saplings, while many common species survived significantly better than average. Some rare or occasional species grew rapidly, either in low—canopy sites or in both canopy—height categories, while most common species grew slowly in both situations. Rare and occasional species had significantly more recruits per adult than did common species, but often this did not balance their higher mortality. Large differences in survival, growth, and recruitment between canopy—height categories were found only among rare and occasional species.