Roger Meltzer, a Cahill Gordon & Reindell partner with an estimated $20 million book of business, has defected to DLA Piper to become the head of corporate finance at the firm, DLA Chairman Frank Burch confirmed Monday.

“This is an opportunity that happens once a decade,” Burch said of Meltzer’s decision to join DLA. “I am personally and professionally thrilled.”

A leading Wall Street M&A lawyer and 29-year Cahill veteran, Meltzer, 56, sat on his former firm’s executive committee. He has represented a wide range of corporate and private equity clients, including BT Securities Corp., Trimaran Capital Partners, and CIBC Wood Gundy Securities Corp.

Meltzer said the move was about finding new challenges, and should not be taken as a sign that anything is wrong at his former firm. “Cahill is a jewel,” he said. “I wanted to do something else.”

Cahill, a 242-lawyer Wall Street firm with gaudy profit per equity partner numbers ($2.57 million in 2006) and a tightly held partnership (63 equity partners), rarely loses partners to anything but retirement.

Meltzer’s job search kicked off eight months ago at dinner with legal recruiter Alan Roberts. According to Burch, Meltzer told Roberts he had risen to the top of his firm in terms of stature, responsibility and compensation, and needed a new challenge.

One of Meltzer’s first meetings was with Burch, and co-CEO Lee Miller. The two-hour conversation was about DLA’s vision of the future of the business of law sector, and about the firm’s commitment to building a global law firm, Burch recalled. “He saw the world they way we do,” Burch said. Over the next few months, Burch had dinner with Meltzer and his wife, entertained him in a suite at a Baltimore Ravens game with firm clients, and introduced him to corporate and finance lawyers in DLA’s London office.

Burch said the hire will help the firm to “continue to evolve up the M&A and capital finance food chain,” particularly in London, New York and Asia.

Meltzer will help leverage relationships with important clients to get more into their finance and M&A work, Burch said. (“We already have identified a number of very large global clients who are interested in meeting Roger,” he said. He declined to say who these clients are.) Meltzer will also serve as a link to private equity and corporate clients he cultivated at Cahill, and will lead efforts to recruit other corporate lawyers, Burch said.

Burch declined to discuss how much Meltzer will be paid at DLA. In 2006 in the U.S., DLA reported profits per equity partner of $1.12 million.

Meltzer told his Cahill partners of his decision Friday morning. Burch said Meltzer told him that the meeting was “quite emotional.” Meltzer said that his partners were supportive. “There was an understanding of what I wanted to accomplish for myself.” Cahill Chairman William Hartnett, reached Friday afternoon, said “it’s always sad when a partner leaves,” and that the firm “wishes him well.”

Burch said Meltzer’s hire is a dividend of the 2004 DLA-Piper Rudnick merger, which announced the firm’s global ambitions. “That was a direct goal, to compete for people like Roger,” Burch said. “If you sat down with a blank sheet of paper and tried to describe the ideal person to take the baton and lead this effort you could not come up with a better candidate.”