New York ? Bob Schieffer will say farewell to viewers of the “CBS Evening News” tonight, but he won’t be doing it alone.

“We may even have a surprise guest – who has a great smile,” Schieffer said, refusing to give more details about the visit.

Viewers, however, shouldn’t be surprised to see Katie Couric, who has been rumored to be dropping by Schieffer’s last telecast for months.

When he does say goodbye, it will mark the end of an 18-month run for Schieffer, who, when asked to step in for the departing Dan Rather, was told it would be a six-week gig.

“It’s going to be emotional for me,” Schieffer said. “This has been a great experience for me.”

Schieffer, who is also the anchor of “Face the Nation,” was asked to step in at a time of great upheaval for CBS News, following Rather’s exit, which itself came months after a controversial story on President Bush’s National Guard history.

“We were in kind of a hard place when I came here,” Schieffer said. “As I look back on it, I feel really good about what we did.”

Under Schieffer, ratings inched up, and for one week last spring, the “CBS Evening News” moved into second place.

Though he’s leaving the “Evening News” anchor slot – Couric will begin Tuesday, after Russ Mitchell fills in on Friday and Monday – Schieffer won’t get lost. He’ll do a commentary piece for Couric’s show on Wednesdays, and he’ll be an analyst for major Washington news stories.

He’ll continue with “Face the Nation” as well.