"The decision to leave the board is a difficult one, because Time Warner is a great company, and I respect Dick Parsons and my fellow directors," said Case. "However, earlier this year, I launched a new company called Revolution, which is building innovative businesses that provide consumers with more choice, convenience and control. Leaving Time Warner's board will give me a greater opportunity to grow Revolution, including avoiding any potential conflicts of interest as Revolution moves into new areas."

Meanwhile, Time Warner continues to endure a dispute with dissident shareholder Carl Icahn. He has pointed to the subscriber drop at AOL as evidence that management hasn't done enough to boost shareholder value. Icahn is urging the New York-based company to fully spin off its cable unit and to buy back $20 billion worth of stock. Time Warner management has said its plan to spin off 16% of the cable business and to buy back $5 billion in stock demonstrates that it is committed to delivering shareholder value.

"On behalf of Time Warner's Board of Directors and senior management team, I thank Steve Case for his years of distinguished service to our company," said Time Warner Chairman Dick Parsons. "We have great respect for his long record of achievement -- as a co-founder of AOL to a valuable member of our board. As Steve is one of our major individual shareholders, we'll look forward to his wise counsel as the company continues to move forward. He will be missed."

Early Monday, Time Warner was up 28 cents to $18.01.

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