The announcement comes a day after AOL Time Warner's America Online unit jettisoned its exclusive arrangement with Monster and.
The back-to-back deals won't directly affect Monster's revenues, which come from employers who pay to place advertisements on its site. But they could cut into its audience reach. AOL and MSN are among the most trafficked destinations on the Web, and a significant number of Monster's 18 million monthly unique visitors currently come by way of those sites.
Monster's stock was down 2 percent, to about $22 a share, in afternoon trading.
For CareerBuilder, a company run by newspaper giants Knight Ridder, Gannett and Tribune Company, the deal marks another coup against rival Web sites that could potentially steal coveted classifieds revenues. Job listings and classifieds are a significant source of revenue for newspapers and a market Web sites have begun targeting.
Online giants such as Yahoo also view online job listings as a potential cash cow. Yahoo last yearin a process that involved outbidding Monster's parent company TMP Worldwide.
CareerBuilder will launch on MSN in January 2004 and will pay the portal up to $150 million over the next five years. The service will launch as part of the MSN Careers channel.