This dissertation research is a multiscale analysis of vascular epiphyte communities in tropical wet forests of northeastern Costa Rica. This study will examine distribution and abundance of vascular epiphytes in relation to their environment at three scales: (1) within individual tree crowns, focusing on the effects of variation in canopy microclimate, (2) among tree species, focusing on the effects of microclimate and tree species characteristics, and (3) among an elevation gradient, focusing on the effects of tree species characteristics and macroclimatic variation. The study will occur in lowland tropical rainforest at La Selva Biological Station and along the adjacent forested elevation gradient in Braulio Carrillo National Park. At La Selva, this work will examine the effects of microenvironmental factors and host tree characteristics on total vascular epiphyte diversity, species composition, and abundance within and among three common canopy tree species. Along the elevation gradient from 30 to 3000 meters, this study will examine macroenvironmental factors that may be linked to species composition in two major epiphyte groups: Bromleiaceae and Pteridophytes. This research will contribute substantially to our knowledge of vascular epiphyte communities, epiphyte diversity in relation to host trees, and ecological distributions of epiphytes with respect to canopy microenvironment and tree characteristics.