This enormous work represents nearly half a century of field research in the Northwest Amazon encompassing parts of Brazil, Colombia, Ecuador, and Peru. While the Northwest region represents only a small part of the entire Amazonian drainage area, it is in many respects the most complex and varied part of the forest; it has also been the least studied.

The authors, from their backgrounds in ethnobotany and phytochemistry, have included and described nearly 1,500 species and variants, representing 596 genera in 145 plant families. Of these, half have had little or no real investigation of their chemical and pharmacological properties.