A patent agent is a person who acts on behalf of an applicant for the purposes of drafting a patent application and then taking that patent application through the various stages needed to grant the patent. While an applicant for patent may file and prosecute his own case, the Patent and Trademark Office usually recommends the use of an attorney or patent agent in filing the application.  Although an inventor may prosecute the application, lack of skill in this field often detracts from obtaining the maximum protection for the invention.  In most inventor-filed cases, the patent Examiner sees that the applicant is unfamiliar with the proper preparation and prosecution, and almost always urges the applicant to employ a registered patent attorney or patent agent to prosecute the application, since the value of a patent is largely dependent upon skillful preparation and prosecution. While the Examiner may recommend hiring an attorney or agent, he never suggests any particular one.

A patent attorney is a qualified attorney-at-law and is technically trained, usually having a degree in engineering or in one or more of the sciences.  A patent agent is also technically trained with a degree in one or more of the sciences but is not an attorney-at-law.  In order to use the title "Patent Attorney" or "Patent  Agent", the attorney or patent agent must satisfy the Commissioner of  Patents of his character and competence in both technology and law and be registered  to practice before the Patent Office, by passing a difficult examination on the preparation, filing and prosecution of patent applications.

Registered Patent Agents
Preparing and prosecuting following through on a patent application is a complex task. Prosecution involves corresponding with the Patent Office, making any necessary amendments to the application, and fixing the legal scope of the patent protection. All this requires broad knowledge of patent law and Patent Office practice—knowledge that you can expect from a specialist known as a registered patent agent. A trained patent agent can save you from many headaches caused by such things as a poorly drafted patent that inadequately protects your invention. Hiring a patent agent is not mandatory but is highly recommended, and most inventors do so.

Registered patent agents must pass rigorous examinations in patent law and practice before they may represent inventors before the Patent Office. Beware of unregistered patent agents; they are not authorized to prosecute applications and are not subject to Patent Office discipline. Patent agents' fees are not regulated by the Patent Office. You and your agent should agree on fees before work on your application begins.

Once you've appointed a patent agent, the Patent Office will correspond with no one else about the prosecution of your application. You may, however, change patent agents at any time. The Patent Office provides a list of registered patent agents but cannot recommend any particular one to you. Your can look up the local telephone directory for patent agent names.