TORONTO, Dec 10 - Goldman Sachs Group Inc (GS.N) will underwrite the Chicago Board Options Exchange's planned share offering, a source familiar with the exchange's thinking said on Thursday.

Directors of the CBOE, the largest U.S. options exchange, approved plans on Thursday to demutualize and complete an initial public offering of holding company CBOE Holdings Inc stock by mid-2010. [ID:nN10201504]

A Goldman Sachs spokeswoman did not immediately comment. (Reporting by Jonathan Spicer; editing by Andre Grenon)