July 30 (Bloomberg) -- Steven Rattner stepped down as the head of DLJ Merchant Banking Partners, the private-equity unit of Credit Suisse Group AG, after more than 20 years at the investment bank once known as Donaldson Lufkin & Jenrette.

Rattner, 48, retired to spend more time with his family, said Suzanne Fleming, a Credit Suisse spokeswoman in New York, who declined further comment. Credit Suisse executive Nicole Arnaboldi was named chairman of the New York-based buyout unit, the company said today in a statement. Rattner couldn't be reached for comment.

DLJ Merchant Banking, which was run by Lawrence Schloss and Thompson Dean before Rattner, raised a $2.1 billion fund, its fourth, in October 2006 and seeks to invest in companies valued at less than $2 billion. Deals of $5 billion or more dried up a year ago as financing costs more than tripled because of the subprime-mortgage crisis.

``There are still some very interesting investing opportunities,'' Arnaboldi said in an interview. ``The leverage levels just aren't there to the degree they were before.''

Arnaboldi, 50, joined DLJ in 1985 and worked in the firm's venture capital business before moving to private equity. She holds a bachelor's degree, a master's degree in business administration and a law degree from Harvard University.

She also will serve as chairman of DLJ Merchant Banking's investment committee and remain co-head of Credit Suisse's illiquid-alternatives business, the company said in the statement. Credit Suisse, based in Zurich, held onto DLJ Merchant Banking as competitors including JP Morgan Chase & Co. spun buyout funds out into independent firms, in part to avoid conflicts with private-equity clients.

Two Decades

Ed Johnson, Kamil Salame, Susan Schnabel and Colin Taylor will form the management committee for DLJ Merchant Banking and report to Arnaboldi.

Rattner, a 1982 graduate of Franklin & Marshall College in Lancaster, Pennsylvania, joined DLJ in 1985 after receiving a law degree from the University of Pittsburgh. He later earned an M.B.A. from New York University. He co-founded the firm's leveraged-finance unit, where he ran sales, trading and capital markets.

He moved to the private-equity group in 2001, a year after Credit Suisse, Switzerland's second-largest bank after UBS AG, bought DLJ in 2000 for $13 billion.

After Schloss and Dean left the firm in 2004 and 2005, respectively, Rattner was promoted to run the group.

DLJ Alumni

Rattner serves on the board of Warner Chilcott Ltd., the Hamilton, Bermuda-based maker of pharmaceuticals including the contraceptive Loestrin.

Other DLJ executives have landed in new Wall Street jobs. Tony James, who served as Credit Suisse's chairman of global investment and private equity, is the president of Blackstone Group LP, manager of the world's largest buyout fund.

Kenneth Moelis left Credit Suisse in 2000 and joined UBS and now runs an advisory firm that bears his name.

Rattner isn't related to Steven Rattner, the co-founder of Quadrangle Group LLC and former deputy chairman of Lazard Ltd.

To contact the reporter on this story: Jason Kelly in New York at jkelly14@bloomberg.net

Last Updated: July 30, 2008 12:27 EDT