Many scientists contend that the Caquetá region in Colombian Amazonia belongs to the most species-rich rain forest areas in the world. This volume in the Tropenbos-Colombia goes a long way to support this claim. The author brings together all existing information on botanical collections made in this region. The number of specimens is over 20,000, and were collected since 1982 in the course of a large number of floristic, ethno-botanical, landscape-ecological, and other studies. Although it is stated that of the entire 1.3 million hectare study area no more than 35 ha. was floristically studied, this yielded the appreciable number of 2,419 species, divided over 777 genera and 178 families. On the basis of these data, the author predicts that the total species number in the middle Caquetá amounts to some 12,000 species. An introductory chapter on climate, soils and vegetation of the region, and a section on its population, precedes the main part of the book: a complete, annotated checklist of all plants. Vernacular names (in Spanish and in various native languages), a short indication of growth form, size, ecology and native uses of the plants complete the checklist.