Changyou.com Limited (Changyou) is an online game developer and operator in the People�s Republic of China. Changyou is engaged in the development, operation and licensing of online games, including massively multiplayer online games (MMOGs), which are interactive online games. It also owns and operates the 17173.com Website, one of the game information portals in China. As of December 31, 2011, the Company operated several MMOGs in China, including the in-house developed Tian Long Ba Bu (TLBB) and Duke of Mount Deer (DMD), and other MMOGs that it has licensed from third parties. As of December 31, 2011, its MMOGs in China had approximately 175.5 million aggregate registered accounts. As of December 31, 2011, its MMOGs in China had approximately 175.5 million aggregate registered accounts. On December 15, 2011, it acquired from Sohu of certain assets of the 17173 Business, which derives revenue primarily from providing advertising services to advertisers on the 17173.com Website.