Apple chief executive Steve Jobs is to take medical leave from his post till the end of June.
Mr Jobs said on Wednesday his health problems had turned out to be "more complex than originally thought."
However, he said he planned to remain involved in major strategic decisions while he's away.
Chief operating officer Tim Cook will take responsibility for day-to-day operations in his absence.
Mr Jobs was diagnosed with pancreatic cancer in 2004.
Last week he sought to soothe persistent concerns about his health, saying a marked weight loss over past months was due to a hormone imbalance that was relatively simple to treat.
