In a letter to Apple staff, jobs said his "hormone imbalance" was now "more complex" and that he'd be stepping back to ensure his team could crack on with new products without the distraction of stories regarding his health.
Stating he would be returning in June Jobs said, "As CEO, I plan to remain involved in major strategic decisions while I am out. Our board of directors fully supports this plan." Apple COO Tim Cook will take his place in the meantime.
What is actually wrong with Jobs remains a mystery. But you can bet that in spite of this statement, there'll be plenty of speculation as to whether he will ever return to the helm at Apple.