Steve Jobs, who died on Wednesday at 56, went on medical leave three times before resigning as CEO:
2004 _ Undergoes surgery to treat a very rare form of pancreatic cancer _ an islet cell neuroendocrine tumor. That type of cancer can be cured if diagnosed early, unlike the deadlier and more common adenocarcinoma. Tim Cook, an executive vice president at the time, runs Apple for two months, although Apple does not disclose Jobs' leave until after the fact.
2009 _ In January, Jobs initially attributes weight loss to a hormone imbalance and says treatment is simple. He backtracks less than two weeks later, however, and announces a six-month medical leave. During that time, he receives a liver transplant that comes to light two months after it was performed. He returns to work in June. Cook, by then the chief operating officer, runs the company during Jobs' absence.
2011 _ Announces medical leave of unspecified duration in January. No details about his condition are given. Cook takes over day-to-day operations, although Jobs returns for public appearances, including the announcement of the iPad 2. Jobs never returns from leave and announces resignation as CEO in August. Apple board elects him chairman.