The Nasdaq Stock Market, Inc. announced that its new centralized trading and negotiation system for private placements (144A securities) begins operating today.

The exchange says that the fully automated Web-based platform is an outgrowth of its existing Portal system, and is the first and only centralized electronic system for displaying and accessing trading interest in 144A issues.

The new Portal system is available to all qualified users. Following today’s launch of a centralized trading and negotiation system for 144A equity securities, Nasdaq anticipates it will phase in debt securities in the fourth quarter.

The new system is intended to improve the efficiency and transparency of the private placement market — thereby encouraging capital formation.

Yesterday, several investment banks announced the creation of their own trading systems for 144A securities.

“The launch of Nasdaq’s Portal trading platform is a milestone in the transformation of the capital raising process in the U.S.,” said Nasdaq executive vice president John Jacobs. “The Portal platform will bring the same efficiency and transparency to the 144A market that Nasdaq brought to public equity trading in the U.S. 36 years ago.”

Nasdaq says that the private placement market has grown substantially in the last five years. It estimates that the amount of equity and debt capital raised using Rule 144A has grown three-fold since 2002 and exceeded $1 trillion in 2006 for the first time. In the first half of 2007, global equity and debt capital raised in conjunction with a 144A tranche was almost $1 trillion, a 43% increase over the first half of 2006. The Portal Market has this year alone designated more than 1,700 144A equity and debt securities as Portal securities, compared to nearly 2,700 in all of 2006.