A practical guide to bark drugs produced by trees and shrubs in the United States, presenting detailed accounts of thirty-five medicinal barks and briefer notes on related species. Species descriptions include botanical features, illustrations, geographic occurrence, harvesting and preparation methods, and distinguishing characteristics for quality and identification. The text indicates which barks are recognized by the official pharmacopoeia and which are used in trade, and it summarizes therapeutic uses, commercial sources, and concerns about forest depletion from bark harvesting. Organized as a field and reference manual, the bulletin aims to assist those engaged in study or collection of medicinal plants.