The filing of a PCT application can be of particular advantage if application for patent is being considered in a large number of countries and/or if it is wished to delay the grant procedure, and the associated costs, as long as possible. By way of a PCT application the time for filing of national and/or regional patent applications can be extended from 12 months to 30 months after the first filing date. Furthermore, the preliminary substantive opinion as to the viability of the patent application can in the meantime be obtained and it is clearer, at the moment when the decision must be taken on filing of possible regional and/or national patent applications, whether enforceable patents can be granted. The PCT application also gives the inventor extra time for commercial development of the invention before the often high costs of the national grant procedures have to be incurred.