Traditional breeding has been widely used in forestry. However, this technique is inefficient because trees have a long and complex life cycle that is not amenable to strict control by man. Fortunately, the development of genetic engineering is offering new ways of breeding and allowing the incorporation of new traits in plant species through the introduction of foreign genes (transgenes). The introduction of selected traits can be used to increase the productivity and commercial value of trees and other plants. For example, some species have been endowed with resistance to herbicide and pathogens such as insects and fungi. Also, it has been possible to introduce genes that modify development and wood quality, and induce sexual sterility. The development of transgenic trees has required the implementation of in vitro regeneration techniques such as organogenesis and somatic embryogenesis. Release of transgenic species into the agricultural market requires a standardized biosafety regulatory frame and effective communication between the scientific community and society to dissipate the suspicions associated with transgenic products.