UPDATE: 6:44 p.M. EST
FOX's Ken Rosenthal tweeted that the Braves still believe they will still get Dempster.
UPDATE: 3:49 P.M. EST:
Ryan Dempster himself has thrown a wrench into the reports below, claiming in a tweet that he has not been traded.
In fact, according to other twitter reports, all appears to be normal.
Ryan Dempster has been traded to the Atlanta Braves, according to tweets from multiple sources.
The exact terms of the deal - including who and/or what the Cubs will get in return - are not yet known for certain. The Cubs were in negotiations with the Los Angeles Dodgers in addition to the Braves, but decided that the Braves offer for Dempster was simply too good to pass up.
Dempster has been named an All-Star twice, in 2000 and 2008. He owns a 5-4 record so far this season with a 2.11 ERA in 15 games as a starter.