Founded in 1987, The Carlyle Group, with $71 billion in assets currently under management, has historically been known as the most politically connected private equity firm, capitalizing on its connections— George Bush Sr. and Jr., Frank Carlucci, John Major, and James Baker III previously served as advisers— to raise funds and secure government contracts.

Founded in 1985, the Blackstone Group has more than $78 billion in assets under management. Blackstone has multiple lines of business in addition to buyouts, including real estate, corporate debt funds, and hedge funds. Blackstone also provides mergers and acquisitions and restructuring advice to corporate clients.

Kohlberg, Kravis, Roberts & Co (KKR) is one of the oldest private equity firms having been founded in 1976, and is known for high-profile deals such as the hostile takeover of RJR Nabisco for $31 billion in 1989, inspiring the bestseller, Barbarians at the Gate. KKR continues to make headlines with announcements of leveraged buy-outs of well-known companies such as First Data and Dollar General.

Founded in 1992, shortly after turning twice-bankrupt Continental Airlines into a serious contender in the airlines market, TPG is regarded as a turnaround expert and specialist in complex investments. In 2006, TPG was involved in $101 billion worth of deals.

As of March 2007, Bain Capital had raised $13 billion in private equity leveraged buyout funds. Bain Capital Inc., formerly Bain & Co., is known for charging higher carried interest than average— 30 percent versus the standard 20 percent—and is a staple of the club deal circuit. Historically, nearly half of Bain’s deals have been club deals.