Patents are generally applied for and granted on a country-by-country basis. Pursuant to the Paris Convention - which has been signed by virtually every industrialized country- a foreign patent application corresponding to a U.S. application may be filed any time within one year after the U.S. patent application filing date and still retain the U.S. application's filing date for priority purposes. This means that a non-U.S. patent application will be treated as if it were filed on the same day as the U.S. application for determining patentability, so that any publication, public use, or sale of the invention occurring after the filing date of the U.S. application is not considered prior art with respect to the foreign patent application.

Although most non-U.S. patents are obtained by filing a patent application with the patent office of each country in which protection is desired, several regional filing systems issue a single patent that is enforceable in any member country. For example, a patent issued from the European Patent Office (EPO) can be enforced in all countries that are members of the European Patent Convention.

A popular option is to file an international patent application under the Patent Cooperation Treaty (PCT) one year after filing the U.S. patent application- rather than a direct national or regional patent application. The PCT route is a convenient way to obtain a patentability search (in Europe or the U.S.) and an initial examination on a single, international patent application. By filing a PCT application, examination costs for each country or region (including obtaining and filing appropriate translations) can be delayed for 18 months. In addition, the results of the examination and the passage of time can enable a better assessment of the patentability - or marketability - of the invention.