Wasserstein was hospitalized earlier this week for an irregular heartbeat, with the company saying Sunday his condition was serious but he was "stable and recovering." In a statement Wednesday, Lazard's board said the cause of death had not yet been determined.
The New York-based firm named Vice Chairman Steven J. Golub as interim CEO, effective immediately. Golub, 63, has been with Lazard since 1984 and served in various senior leadership positions, including as CFO and chairman of Lazard's financial advisory business.
But some say Lazard's success was so tied to Wasserstein that the company could face a tough road ahead.
"Mr. Wasserstein was the main driver that created Lazard as a public company," Rochdale Securities analyst Richard Bove said. "He forced the expansion of the business and his contacts brought in deals. He cannot be replaced easily or perhaps at all."
Collins Stewart LLC analyst William Tanona, however, said Lazard has a deep management bench, and expects the company to post improved profit as the merger and acquisition environment improves. Tanona said he does expect the company's stock to sell off in the wake of Wasserstein's death but is advising investors to take advantage of the opportunity to build positions.
A Wall Street superstar since the 1980s, Wasserstein worked on such landmark deals as Kohlberg Kravis Roberts' takeover of RJR Nabisco, and the Morgan Stanley-Dean Witter and AOL-Time Warner mergers. Most recently he was advising Kraft Foods Inc. on its unsolicited $16.7 billion takeover bid for British candy maker Cadbury PLC.
In the 1980s, Wasserstein and Joseph Perella ran First Boston Corp.'s mergers and acquisitions department before leaving to form their own boutique investment bank, Wasserstein Perella Group Inc. It was at Wasserstein Perella that the pair worked on the RJR Nabisco deal, at the time the biggest corporate takeover in U.S. history, with a price tag of $24.5 billion.
The deal was chronicled in the 1990 book "Barbarians at the Gate," by journalists Bryan Burrough and John Helyar, and later made into an Emmy award-winning television movie starring James Garner as RJR Nabisco CEO F. Ross Johnson.
Wasserstein was CEO of Wasserstein Perella between 1988 and 2001 before selling it to Germany's Dresdner Bank AG for about $1.4 billion.
Wasserstein joined Lazard in 2002 with a mission to turn the investment bank around, and make it more competitive against bigger firms like Goldman Sachs Group Inc. and Morgan Stanley. He took the company public in May 2005, and continued to drive a series of high-profile deals. In 2006, he led a controversial report which agreed with billionaire investor Carl Icahn that Time Warner should be broken up into four companies _ AOL, Time Warner Cable, publishing and entertainment _ amid shareholder dissatisfaction with the outcome of the AOL-Time Warner merger, a deal with which he had been involved.
Lazard has remained relatively strong throughout the economic downturn. Its second-quarter profits fell 18 percent to $28.2 million, or 34 cents per share, but easily surpassed expectations. Lazard's financial restructuring business has thrived during the downturn, offsetting declines in mergers and acquisitions advisory business.
"We are shocked and greatly saddened by the passing of Bruce Wasserstein. He was a visionary leader, a devoted father to his children and a good friend," the company's board said Wednesday.
Aside from his work at Lazard, Wasserstein was chairman of Wasserstein & Co., a private investment firm, which targets investments betwen $30 million and $150 million. It has investments in companies ranging from Penton Media Inc., a publisher of trade magazines, to gourmet food seller Harry & David.
Wasserstein also owns New York Media Holdings LLC, which publishes New York magazine.
Forbes magazine estimates Wasserstein's net worth at $2 billion.
Former New York City public advocate Mark Green, one of Wasserstein's Harvard Law classmates and fellow former volunteer for Ralph Nader's consumer advocacy group in the 1970s, said in a statement Wednesday that Wasserstein used his great analytical skills to advise businesses how to be both responsible and profitable.
"No one did it better," Green wrote. "He earned the trust and respect of both the consumer side and the business side. He had a deep laugh, an agile mind and loved the game of business and of politics. I've never met anyone with a better sense of strategy."
Wasserstein was the brother of Wendy Wasserstein, a Tony award and Pulitzer Prize-winning playwright who died in 2006. Her plays included "The Heidi Chronicles" and "The Sisters Rosensweig." He is survived by his wife and children, including the daughter of his late sister Wendy, The New York Times said Wednesday.