‘Trademark Dilution Doctrine’ is basically a trademark law concept that permits the owner of a famous mark to forbid others from using that mark in a way which would harm its uniqueness. A trademark is diluted when the use of similar or identical trademarks in other noncompeting markets means that the trademark in and of itself will lose its capacity to signify a single source. In other words, unlike ordinary trademark law, dilution protection extends to trademark uses that do not confuse consumers regarding who has made a product. Instead, dilution protection law aims to protect sufficiently strong trademarks from losing their singular association in the public mind with a particular product, perhaps imagined if the trademark were to be encountered independently of any product. The aim of this paper is to study in detail this doctrine as it stands today after the enactment of the Trademark Dilution Revision Act 2005 in the United States, and indicate key issues which require detailed inquiry and analysis.