Epiphytes have epitomized a neutral, or commensalistic symbiosis with their hosts, and have historically been considered to only minimally affect the nutrient relations of supporting trees and the ecosystem as a whole. Research in the last decade, however, has revealed that epiphytes may significantly contribute to overall nutrient cycling despite their biomass being small, relative to the ecosystem as a whole. This has been confirmed in various forests, ranging from dry temperate oak woodland to very wet neotropical cloud forests. A general model to enumerate the inputs, pools, and outflows of mineral nutrients of the epiphyte component is presented. Studies on the effects of epiphytes on nutrient transfers from epiphytes to other ecosystem members from a temperate and a tropical rainforest show that epiphytes tend to absorb atmospheric-borne nutrients during the dry season. During the wet season, there is a greater net release of nutrients from branches with epiphytes than from those whoe epiphytes had been experimentally stripped. Mechanisms by which epiphytes may enhance the nutrient status of individual host trees and the forest as a whole are summarized.