It is well recognized throughout the World that one must register a trademark in order to claim exclusive use of such. Mexico´s Industrial Property Law(LPI) accords great value to the use of trademarks, including use before they are registered. In this sense, the LPI establishes that the registration of atrademark does not take effect against third parties who, in good faith, previously used the same or similar trademark for equal or similar products orservices, so long as such third party user can show that it began using the trademark before the date of filing the trademark registration application or thedate of first use declared by the registered trademark´s owner. Additionally, the LPI establishes that the trademark registration will be declared null if athird party proves that it has used the same trademark in Mexico, or abroad, prior to the date of the filing of the trademark application or the date of firstuse declared by the trademark's owner. In all cases, it is worth noting that the ability to present a trademark nullity lawsuit against a registeredtrademark for prior use may be pursued within three (3) years following the date of publication of the trademark registration in Mexico.