Several developments have contributed to the discovery that patents are an invaluable source of scientific information: the new accessibility via computerized databases, the expanded coverage of patents into such areas as biotechnology, computer programs, and live animals, improved formats, easier to read text, and expanded bibliographic control. Walker describes the many uses for information found in patents, followed by details of their availability from around the world and the many printed, online, and CD-ROM services designed to make them accessible. Searching techniques and strategies are given to facilitate the use of both subject files and those covering patents exclusively. Librarians and information scientists in general science and technical collections as well as patent searchers in a variety of information agencies will find valuable information in this comprehensive treatment of patent sources.