These two great old rivals, 78-year-old Viktor Korchnoi and 72-year-old former World Champion Boris Spassky, are playing what is at least the fourth match of their illustrious rivalry. The first two were the most important: a Candidates Final won by Spassky in 1968 and another Candidates Final won by Korchnoi in 1977. In 1999 they played a surprisingly bloodthirsty rapid match (won by Korchnoi with a +4 -2 =4 score), and now they're at it again.
It's an eight game match, and you can find more information, along with the games (downloadable in PGN or available on a replayable board) here. Korchnoi won game 1.