Secondary forests are a vital part of the tropical landscape, and their worldwide extent and importance continues to increase. Here, we present the largest chronosequencedata set on forest succession in the wet tropics that includes both secondary and old-growth sites. We performed 0.1 ha vegetation inventories in 30 sites in northeasternCosta Rica, including seven old-growth forests and 23 secondary forests on former pastures, ranging from 10 to 42 yr. The secondary forest sites were formerly pasture forintervals of o 1–25 yr. Aboveground biomass in secondary forests recovered rapidly, with sites already exhibiting values comparable to old growth after 21–30 yr, andbiomass accumulation was not impacted by the length of time that a site was in pasture. Species richness reached old-growth levels in as little as 30 yr, although sites thatwere in pasture for 4 10 yr had significantly lower species richness. Forest cover near the sites at the time of forest establishment did not significantly impact biomass orspecies richness, and the species composition of older secondary forest sites (4 30 yr) converged with that of old growth. These results emphasize the resilience of tropicalecosystems in this region and the high conservation value of secondary forests.