Among the wild plants of the United States are many that have long been used in the practice of medicine, some only locally and to a minor extent, but others in sufficient quantity to make them commercially important. The collection of such plants for the crude-drug market provides a livelihood for many people in rural communities, especially in those regions where the native flora has not been disturbed by agricultural or industrial expansion and urban development. There is an active interest in the collection of medicinal plants because it appeals to many people as an easy means of making money. However, it frequently requires hard work, and the returns, on the whole, are very moderate. Of the many plants reported to possess medicinal properties, relatively few are marketable, and some of these are required only in small quantities. Persons without previous experience in collecting medicinal plants should first ascertain which of the marketable plants are to be found in their own locality and then learn to recognize them. Before undertaking the collection of large quantities, samples of the bark, root, herb, or other available material should be submitted to reliable dealers in crude drugs to ascertain the market requirements at the time and the prevailing prices. To persons without botanical training it is difficult to describe plants in sufficient detail to make identification possible unless such descriptions are accompanied by illustrations. It is the purpose of this publication to assist those interested in collecting medicinal plants to identify such plants and to furnish other useful information in connection with the work.