The PCT was concluded in 1970, amended in 1979, and modified in 1984 and 2001.
It is open to States party to the Paris Convention for the Protection of Industrial Property (1883). Instruments of ratification or accession must be deposited with the Director General of WIPO.
The Treaty makes it possible to seek patent protection for an invention simultaneously in each of a large number of countries [PDF] by filing an "international" patent application. Such an application may be filed by anyone who is a national or resident of a Contracting State. It may generally be filed with the national patent office of the Contracting State of which the applicant is a national or resident or, at the applicant's option, with the International Bureau of WIPO in Geneva. If the applicant is a national or resident of a Contracting State which is party to the European Patent Convention, the Harare Protocol on Patents and Industrial Designs (Harare Protocol), the revised Bangui Agreement Relating to the Creation of an African Intellectual Property Organization or the Eurasian Patent Convention, the international application may also be filed with the European Patent Office (EPO), the African Regional Industrial Property Organization (ARIPO), the African Intellectual Property Organization (OAPI) or the Eurasian Patent Office (EAPO), respectively.
The international application is then subjected to what is called an "international search." That search is carried out by one of the major patent offices appointed by the PCT Assembly as an International Searching Authority (ISA). The said search results in an "international search report," that is, a listing of the citations of such published documents that might affect the patentability of the invention claimed in the international application. At the same time, the ISA prepares a written opinion on patentability.
The international search report and the written opinion are communicated by the ISA to the applicant who may decide to withdraw his application, in particular where the said report or opinion makes the granting of patents unlikely.
If the international application is not withdrawn, it is, together with the international search report, published by the International Bureau.
The procedure under the PCT has great advantages for the applicant, the patent offices and the general public:
(i) the applicant has up to 18 months more than he has in a procedure outside the PCT to reflect on the desirability of seeking protection in foreign countries, to appoint local patent agents in each foreign country, to prepare the necessary translations and to pay the national fees; he is assured that, if his international application is in the form prescribed by the PCT, it cannot be rejected on formal grounds by any designated Office during the national phase of the processing of the application; on the basis of the international search report or the written opinion, he can evaluate with reasonable probability the chances of his invention being patented; and the applicant has the possibility during the international preliminary examination to amend the international application to put it in order before processing by the designated Offices;
(ii) the search and examination work of patent offices can be considerably reduced or virtually eliminated thanks to the international search report, the written opinion and, where applicable, the international preliminary examination report that accompany the international application;
(iii) since each international application is published together with an international search report, third parties are in a better position to formulate a well-founded opinion about the patentability of the claimed invention.
The PCT created a Union. The Union has an Assembly. Every State party to the PCT is a member of the Assembly.
Among the most important tasks of the Assembly are the amendment of the Regulations issued under the Treaty, the adoption of the biennial program and budget of the Union and the fixing of certain fees connected with the use of the PCT system.
Details concerning the PCT can be most simply obtained by consulting the Protecting your Inventions Abroad: Frequently Asked Questions about the Patent Cooperation Treaty [PDF], the PCT Applicant's Guide and the PCT Newsletter, published by WIPO.