The future leadership of the Apple computer empire was unclear last night after its chief executive, Steve Jobs, took six months' medical leave to tackle deteriorating health.
Nine days after reassuring staff and investors that he had nothing more than a hormonal imbalance, Jobs stunned the technology community by disclosing that his medical issues were "more complex" than he initially thought.
In an email to staff, Jobs said Apple's chief operating officer, Tim Cook, was taking day-to-day charge of the business until the end of June. But Jobs said he would remain involved in "major strategic decisions" throughout his time out.
On Wall Street, trading in Apple's shares was briefly suspended by the technology-dominated Nasdaq stockmarket while the company issued the news. When action resumed, the stock slumped by 9%.
Jobs, 53, co-founded Apple in 1976 and is widely viewed as the driving force behind consumer electronics blockbusters such as the iMac, the iPod and the iPhone. His wealth is estimated at $5.4bn (£3.7bn) by Forbes magazine, ranking him as the world's 189th richest man.
He had surgery for pancreatic cancer in 2004 and appeared to have beaten the disease. But Jobs' health has been the subject of intense speculation since he appeared at a technology conference in the summer looking gaunt and drawn.
In his email to employees, Jobs said: "Unfortunately, the curiosity over my personal health continues to be a distraction not only for me and my family, but everyone else at Apple as well. In addition, during the past week I have learned that my health-related issues are more complex than I originally thought. In order to take myself out of the limelight and focus on my health, and to allow everyone at Apple to focus on delivering extraordinary products, I have decided to take a medical leave of absence until the end of June."
Jobs' health is viewed as a critical issue by investors who are increasingly nervous about the company's lack of disclosure. For months, Apple insisted that Jobs was in good health until last week's announcement that his recent weight loss was down to a "nutritional problem" caused by an easily treatable hormone imbalance.
Jobs is answerable to a heavyweight board of directors which includes the former US vice-president Al Gore, the Google chief executive Eric Schmidt, and the head of Avon cosmetics, Andrea Jung. Questions were mounting last night over the company's corporate governance.
"People are going to be very frustrated with the way Apple handled this," said Gene Munster, a technology analyst at stockbroker Piper Jaffray.
Munster added, however, that as Jobs' long-standing right-hand man, Cook was well qualified to fill in as chief executive: "He's very capable of running the company, although obviously, replacing the magic of Steve Jobs is impossible."
With a market value of $75bn, Apple is one of the world's most successful technology firms. The business was established by Jobs and a friend, Steve Wozniak, in Jobs' parents garage in California.
A university drop-out, Jobs has always eschewed the usual corporate uniform, typically preferring to appear in jeans and a polo-necked sweater. He is a vegetarian, Buddhist and a father of four.
Under Jobs' leadership, Apple has stolen a march on its rivals through its simple, sleek, easy-to-use designs for music players, computers and phones. The company is highly profitable – it earned $4.8bn on sales of $32bn in the year to November.
