Previously, Web users could see the Top 10 list only by going directly to the FBI home page. The list has been online since 1995.
Since Wednesday, visitors to the Lycos homepage can see a banner ad that changes periodically to a wanted ad. They can click on it to go to the FBI's Web site for more information about the criminals on the most wanted list.
Gail Marcinkiewicz, a special agent and spokeswoman for the FBI in Boston, said: "The more we put things out there in the media, the more likelihood of success."
The FBI is not paying for the ads, which are being displayed as a public service by Terra Lycos.
Similar listings could follow on other Web sites, she said.
Mark Stoever, vice-president of operations for Terra Lycos in the US, said the online pop-up ads could be more effective because they can be updated on the fly.
The wanted ads will be distributed in English across the Lycos Network around the world and in Spanish on Terra.com, which draws heavy Internet traffic from Latin America.
The Terra Lycos network of sites includes Terra in 17 countries, Lycos in 25 countries, Angelfire.com, Maptel.com, Matchmaker.com, Quote.com, RagingBull.com, Rumbo.com, Tripod.com and Wired.com.