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Patent Law Research Guide: Patent Search

Patent & Trademark Resource Center Library

Reading a Patent

See Brown & Michaels How do I Read a Patent

Current Challenges in Patent Information Retrieval

Why Search Patents?

  • To determine whether your invention meets the requirements for patentability under 35 USC 101 - 103:  Novel, non-obvious, useful  (“Patentability Search”)*
  • To determine areas of opportunity (State of the Art search)
  • To determine whether a product infringes an existing patent (Infringment Search)
  • To determine whether an existing patent is valid in light of already published prior art. (Validity Search).
  • To do research on a company.

Patentability Search: What to Examine

Examine prior art, which is any publication in the public domain.   Prior art includes:

  • Published patent applications  - U.S. and foreign
  • Granted patents - U.S. and foreign
  • Non-patent literature - journals, papers, web sites, manuals, patent landscape reports, etc. 

For details on what constitutes prior art, see Manual of Patent Examining Procedure, 900


Search by Patent Classification

You will want to search by CLASSIFICATION in order to get more results than a keyword search, and for increased accuracy.  

Classification Systems:

On January 1, 2013 the US PTO began using the Cooperative Patent Classification (CPC) system for published utility patent applications. In January 2015 the US PTO is scheduled to use the CPC for granted utility patents as well as published applications.

See the USPC-to-CPC Concordance Tool on the U.S. Patent and Trademark OFfice website.

Search by Cross-Reference

You will also want to search by CROSS-REFERENCE to be thorough.  Once you find a relevant patent, see what patents and classification numbers are referred to by the patent.  

Shepardizing/Keyciting Patents

Keep in mind that you can Shepardize or Keycite a patent to turn up cases, litigation documents and related patents.

(Format for shepardizing - shep: patno 6553350)

The USPTO's Seven Step Process - a summary

  1. Write out keywords to use to find classifications.
  2. Search USPTO site to find patent classifications
  3. Verifty the relevance of patent classifications by viewing the definition, if that classification has a definition
  4. Retrieve granted patents with those classifications numbers -  Pick out the most relevant ones.
  5. Review in depth the patents you selected above.  Pay close attention to the additional drawings pages, the specification and especially the claims. References cited by the applicant and/or patent examiner may lead you to additional relevant patents.  Look at Current U.S. Class and Current International Class to see if any more classes apply.
  6. Retrieve published patent applications with classifications you selected.
  7. Broaden your search to find additional U.S. patent publications using keyword searching in PatFT or AppFT databases, classification searching of non-U.S. patents on the European Patent Office's Worldwide Espacenet patent database ( is external)) and searching non-patent literature disclosures of inventions using the free electronic and print resources of your nearest Patent and Trademark Resource Center (

See the USPTO's Seven Step Strategy

Historical Searching by Inventor Name

Thomas Edison

Thomas Edison. Photo courtesy of Wikipedia

Free Patent Search Sites

International Patent Offices - with Free Searches

Commercial Databases for Patent Searching

Commercial databases offer easier searching with more whistles and bells than the freely available databases.

There are other very sophisticated databases that the law school does not subscribe to, such as:

Video: How to Search for Patents

More Videos on Patent Research

Patent Searching How-to Documents

Searching for Patents owned by a Company

  • Patents may be in the name of a Patent Holding Company, not the Corporation.  
  • On the company's website, search for managers or employees with "technology" or "research" in their title, and search these names as an inventor.
  • Run a trademark search for the company's product and find the owner (search as assignee).