You can establish rights in a mark based on legitimate use of the mark. However, owning a federal trademark registration on the Principal Register provides several advantages, e.g.,

• constructive notice to the public of the registrant's claim of ownership of the mark;

• a legal presumption of the registrant's ownership of the mark and the registrant's exclusive right to use the mark nationwide on or in connection with the goods and/or services listed in the registration;

• the ability to bring an action concerning the mark in federal court;

• the use of the U.S registration as a basis to obtain registration in foreign countries; and

• the ability to file the U.S. registration with the U.S. Customs Service to prevent importation of infringing foreign goods.
  

Bear in mind, therefore, that if you are currently using a mark and do not register it with the USPTO, a newcomer using the exact same mark in another part of the country could enter your territory with a federal trademark registration for the identical mark you are using, will then have federal protection, and could bring expensive litigation against you over the mark.  Not only could you incur unnecessary litigation expenses, you could suffer losses from any investments you have made in your business and take away any goodwill you have nurtured with your client base. 

For more information about registering your mark, please see the "Fees" link on the left.

ITU Applications

If you have a bona fide intention to launch a product or service in the next six months and you intend to use a mark in connection with those products or services in interstate commerce, it is advisable that you file an Intent To Use Application (the “ITU Application”) with the USPTO,  The upside of filing an ITU Application is that it preserves your rights against others throughout the United States even though you have yet to launch your new product or service in the next six months.  By filing an ITU Application, you may preserve your trademark rights over others who could apply for the same mark within the six-month period.  You will also have the ability to file an Extension of Time form to actually use the mark for an additional fee.  Every six months, you can file an extension with the PTO for yet another six months up to three years (if you comply with certain PTO requirements) to keep your application alive.  Once you actually use the mark, you will then need to file an Allegation of Use, which requires an additional fee. 

For more information about filing ITU Applications, please see the "Fees" link on the left. 

* Adapted from the USPTO website.