Trying to keep the Michael Phelps glow, NBC has agreed to televise next year’s World Swimming Championships from Rome, along with the 2009, 2010, and 2011 national championships.

The deal, announced Thursday, is NBC’s latest attempt to ride the wake of the Olympic golden boy’s race to history. In large part because of Mr. Phelps’s successful attempt to win eight gold medals in Beijing, NBC Universal’s Olympic telecasts have been a ratings success.

NBC has been advertising its own DVD of Phelps highlights since less than a half-hour after he earned his eighth medal. No immediate sales figures were available. The swimming star will also make an appearance from London during Sunday’s closing festivities, NBC said. London is the site of the 2012 Olympics.

And guess who has already signed on to appear at this winter’s Super Bowl, also broadcast by NBC?

The swimming championships will be shown on NBC for the first time. The network already has the rights to the 2012 U.S. Olympic swimming trials and the London Games.

NBC Universal, owned by General Electric Co., will top its ratings from the Athens Olympics four years ago — an unusual feat in today’s TV world. During the half-hour that Mr. Phelps raced for his eighth gold medal, NBC had 39.9 million viewers. More people were interested in that relay than in finding out the next “American Idol” or winners of this year’s Academy Awards.