Abstract
La Amistad International Park is a World Heritage Site, which comprises 401,000 ha of mainly upland continuous natural vegetation straddling the Costa Rica and Panama border. We present a first checklist of vascular plant diversity for the park and a brief discussion of how this diversity is distributed by elevation and vegetation type together with a superficial assessment of floristic affinities. The checklist recognises 3,046 vascular plant species, 26 of which are lycopods, 433 are ferns and 2,586 are seed plants. Of these, 16 are new records for Costa Rica and 39 are for the flora of Panama; 14 represent undescribed or new species to science and 73 are endemic to La Amistad or its buffer zone. For each species we document its presence within the Park by citing herbarium specimens and the associated elevational range, together with their global distribution, extinction risk assessments where undertaken, whether the taxon is exotic.