"At my request, the board of directors has granted me a medical leave of absence so I can focus on my health," Jobs said in an e-mail to employees. "I will continue as CEO and be involved in major strategic decisions for the company."
The reason for the medical leave of absence was not stated. Jobs underwent a liver transplant in 2009.
Jobs said he tapped Chief Operating Officer Tim Cook to head Apple's day-to-day operations.
"I have great confidence that Tim and the rest of the executive management team will do a terrific job executing the exciting plans we have in place for 2011," Jobs said.
Jobs said he hoped to return to work as soon as possible, and asked that his and his family's privacy be respected.