Inventors may prepare their own applications and file them in the Patent and Trademark Office, however, unless they are familiar with the Patent Office rules and regulations, they may get into considerable difficulty. While a patent may be obtained in many cases by persons not skilled in this work, there would be no assurance that the patent obtained would adequately protect the particular invention.

Most inventors employ the services of registered patent attorneys or patent agents. The law gives the Patent and Trademark Office the power to make rules and regulations governing conduct and the recognition of patent attorneys and agents to practice before the Patent and Trademark Office. Persons who are not recognized by the Patent and Trademark Office for this practice are not permitted by law to represent inventors before the Patent and Trademark Office. To be become registered to practice patent law as a patent attorney or patent agent, requires a showing that the person is of good moral character and of good repute and that he/she has the legal, and scientific and technical qualifications necessary to render applicants for patents a valuable service. Certain of these qualifications must be demonstrated by the passing of an examination. Those admitted to the examination must have a college degree in engineering or physical science or the equivalent of such a degree. 

The Patent and Trademark Office registers both attorneys at law and persons who are not attorneys at law. The former persons are now referred to as "patent attorneys" and the latter persons are referred to as "patent agents". Insofar as the work of preparing an application for a patent and conducting the prosecution in the Patent and Trademark Office is concerned, patent agents are usually just as well qualified as patent attorneys, although patent agents cannot conduct patent litigation in the courts or perform various services which the local jurisdiction considers as practicing law. For example, a patent agent could not draw up a contract relating to a patent, such as an assignment or a license, if the state in which he/she resides considers drafting contracts as practicing law.