Classification searching utilizes the U.S. Patent Classification system (USPCS) which has been used and updated by the USPTO for over 100 years. The system organizes patents by the features of the invention described in the patents. For example, all patents for pickup truck bed liners will be found in the same classification regardless of the actual words used to describe them.

Classification searches cover all utility, design and plant patents issues by the U.S. Federal government (1790 to present) and patent applications published by the USPTO (April 2001 to present). This search method does not include foreign patents or other forms of technological information, such as technical publications, scientific journals, trade catalogs, and books. Additionally, this search method does not cover information regarding specialized search tools provided by outside parties such as Chemical Abstracts or DIALOG Information Services.

Advantages: Since classification searching relies on the features of a patent, rather than the words used to describe the patent, all patents that utilize specific features will be returned as a search result. Additionally, classification searches will retrieve all patents from 1790 to present; there is no date restriction.

Disadvantages: Searchers new to the concept of classification searching will ideally spend time learning how to find and use classifications to retrieve patents. Also, the development of new classifications is a reactive process which means that the USPTO develops new classifications as a result of new patent trends. Consequently, new searchers may have difficulty finding patents in very new technological areas.

(These links require Macromedia's Flash player.)
Steps for searching by classification on the USPTO website:

		Index to the U.S. Patent Classification
		Manual of Classification
		Classification Definitions
		List of Patents