Felipe Massa beat his title rival Lewis Hamilton to the fastest time in opening practice at Interlagos, after a very close battle between the championship combatants.
It was McLaren driver Hamilton who held the advantage for most of the session, which took place on a mostly dry track occasionally made slippery by drizzle, before Massa's Ferrari edged ahead by 0.190 seconds in the closing minutes.
The title contenders remained in the garages for the first half of the session, allowing the Toro Rossos, Renault's Nelson Piquet and Toyota's Timo Glock to lead the way early on.
But once the front-runners emerged, it was Hamilton who got up to speed fastest, quickly putting in a 1:12.495 to move to the head of the times.
Massa appeared to lack the McLaren's first lap pace, but edged ever closer - narrowing Hamilton's advantage first to 0.193 seconds, then 0.062, 0.047 and eventually 0.014 seconds.
With the light but persistent spots of rain starting to make the track treacherous, it looked like Massa might have to settle for a tantalisingly close second place, but the Brazilian then threw in a 1:12.305 on his final run to beat Hamilton by nearly two tenths of a second.
The Briton was unable to respond, locking his brakes and flat-spotting a tyre on his next flying lap.
Raikkonen, who had a quick spin when the track was at its slickest, was just 0.012 seconds slower than Hamilton in third place, with BMW's Robert Kubica pushing Hamilton's McLaren teammate Heikki Kovalainen back to fifth.
Renault duo Fernando Alonso and Piquet took sixth and eighth, split by Red Bull's Mark Webber, as the final top ten spots fell to Nick Heidfeld (BMW) and Glock.
Pos Driver Car Time Laps 1. Massa Ferrari (B) 1:12.305 24 2. Hamilton McLaren-Mercedes (B) 1:12.495 + 0.190 23 3. Raikkonen Ferrari (B) 1:12.507 + 0.202 18 4. Kubica BMW Sauber (B) 1:12.874 + 0.569 24 5. Kovalainen McLaren-Mercedes (B) 1:12.925 + 0.620 20 6. Alonso Renault (B) 1:13.061 + 0.756 25 7. Webber Red Bull-Renault (B) 1:13.298 + 0.993 24 8. Piquet Renault (B) 1:13.378 + 1.073 39 9. Heidfeld BMW Sauber (B) 1:13.426 + 1.121 28 10. Glock Toyota (B) 1:13.466 + 1.161 33 11. Trulli Toyota (B) 1:13.600 + 1.295 24 12. Rosberg Williams-Toyota (B) 1:13.621 + 1.316 23 13. Bourdais Toro Rosso-Ferrari (B) 1:13.649 + 1.344 30 14. Barrichello Honda (B) 1:13.676 + 1.371 28 15. Button Honda (B) 1:13.766 + 1.461 13 16. Nakajima Williams-Toyota (B) 1:13.806 + 1.501 24 17. Vettel Toro Rosso-Ferrari (B) 1:13.836 + 1.531 30 18. Coulthard Red Bull-Renault (B) 1:13.861 + 1.556 19 19. Sutil Force India-Ferrari (B) 1:14.704 + 2.399 21 20. Fisichella Force India-Ferrari (B) 1:14.821 + 2.516 21 All timing unofficial