Apple chief executive Steve Jobs is back at work, according to a company statement, ending weeks of speculation about his return.
He has been on six months' medical leave, during which he had liver transplant surgery.
Jobs had surgery in 2004 for pancreatic cancer, which medical experts have said explains the liver transplant.
The statement released yesterday said Jobs is at Apple only a few days a week and will be working at home on the remaining days.
Apple gave no details about how much Jobs planned to work each day or about his current medical condition or recovery from the liver transplant.
Analysts say Apple is likely to give the bare minimum of information for as long as possible, but warned investors should remember that Jobs' health remains a risk.
Apple's share price dropped 47 cents yesterday to close at $141.97, but analysts say the market has not yet had time to digest news of Jobs' return to work.
In the first week of June, the Wall Street Journal said Jobs was expected to return to work soon, sparking speculation that he would unveil the iPhone 3GS at Apple's Worldwide Developers Conference on 8 June.
On 22 June, Jobs was quoted for first time in a press release since going on medical leave.
The release included comments from Jobs about the iPhone. "With over 50,000 applications available from Apple's revolutionary App Store, iPhone momentum is stronger than ever," he said.