55-year-old Apple CEO Steve Jobs told staff that he had been granted medical leave "so I can focus on my health" without providing further details.
The leave is Jobs' third stint off work on medical grounds and again sees COO Tim Cook step into the breach although Jobs said he would still take part in "major strategic decisions for the company."
"I love Apple so much and hope to be back as soon as I can. In the meantime, my family and I would deeply appreciate respect for our privacy," Jobs told staff in an email.
Unless Jobs' time off is short the move makes it likely that Apple's charismatic front man will not be available when the firm launches the second generation iPad, widely tipped to appear in a few weeks time.
Wall Street's valuation of the iPhone-maker is highly dependent on Steve Jobs. The last time Jobs went on leave following pancreatic cancer treatment in 2009, Apple's valuation plummeted 10 per cent and trade was suspended.
The lack of a management succession plan has also been criticised by analysts and will doubtless contribute to the pummeling Apple stock is set to face as trade resumes on Tuesday.
Unlike Jobs' medical leave of absence in 2009, Jobs didn't mention a return time frame which will likely result in further speculation and a mounting calls from shareholders to clarify succession plans.
The eventual hiring of a new Apple front man not be considered lightly given that Jobs' job is one of the highest profile IT executive roles in the industry.