There are about one thousand species of woody plants that occur naturally on the Horn of Africa, including trees and large shrubs, and they have many functions in the highly varied ecosystem on the Horn, including soil conservation and the prevention of flooding during tropical rainstorms. For historical reasons, the woody flora and the vegetation types they form have been less studied than in most other parts of Africa, and new species of even rather large shrubs or trees are still discovered, named and described. This project, which is part of an involvement with the flora and vegetation on the Horn since 1970, aims at describing and mapping the woody plants, the vegetation types they form, and the ways in which the local population interacts with them. The nearer aims are to produce manuals and scientific publications on the flora, including an improved map of the vegetation. Due to long-term collaboration with Ethiopian scientists and the involvement of many Ethiopian Ph.D. students, some of which will eventually become staff members at the new universities of the country, we have as an aim for the future to spread the information not only in international academic circles, but also to relevant places in the vast countries of the Horn.