Nico Rosberg returned to the slot he has made his own this season, finishing at the top of the timesheets in Thursday's second practice for the Monaco GP.
The German clocked a 1:15.446 to lead the way ahead of the McLaren of Lewis Hamilton, who put in a stellar performance, often holding down the P1 slot himself.
Third place went to the Brawn GP of Rubens Barrichello, who outpaced team-mate Jenson Button while Felipe Massa and Sebastian Vettel completed the top six.
Report: Sebastien Buemi, the two Force Indias and Nelson Piquet Jr were the early starters as they ventured out almost immediately for their installation laps. Meanwhile Mark Webber was left stuck on the sidelines for at least "twenty minutes, half an hour" due to a vibration coming from the back of his car that his mechanics were furiously working to fix. The Aussie, though, insisted it had nothing to do with the double-decker diffuser that Red Bull are running for the first time this weekend.
Buemi set the first time of the session, a 1:23.542. Bourdais joined the running, beating his team-mate's time only to be knocked down a lap later. Nico Rosberg took the early P1 slot with a 1:19.433.
Problems for Robert Kubica as a huge plume of smoke rose from his stricken BMW, which expired in spectacular style up the hill from Ste Devote. Yellow flags were brought out at the marshalls craned his car out of harm's way.
Heikki Kovalainen went second ahead of Kazuki Nakajima, Bourdais, Buemi, Fernando Alonso, Adrian Sutil and Nelson Piquet. Kovalainen moved up to first place while Felipe Massa took third before he was dropped by team-mate Kimi Raikkonen. The two Ferraris fell further as Lewis Hamilton improved to second and then first. Raikkonen moved up to second.
Barrichello, who was quickest in Prac One, put in a flier to take third place despite a few tussles with his BGP001. Piquet took first place before his team-mate Alonso overhauled him. Trulli slotted in between the two Renaults before Barrichello took second off him. Nakajima moved up to fourth and then took first.
Kovalainen is the next to take the P1 slot as he posted a 1:16.871. Alonso took second place behind him while Hamilton improved to fourth and then second. Massa displaced Kovalainen at the top of the timesheets before he too was dropped by Hamilton. Raikkonen slotted in ahead of Massa, just a tenth slower than Hamilton.
The drivers continued to put in the laps with Hamilton leading the way and the rest fighting amongst themselves for second place. It went to Barrichello, then to Raikkonen, only for Barrichello to improve to P1 ahead of Hamilton. Kovalainen and Massa followed suit.
Rosberg went on a charge and took second place while Raikkonen improved to sixth behind Hamilton and Button. Hamilton moved up to second before Rosberg dropped him by taking the P1 slot with a 1:15.446.
The Williams driver ended the session in P1, followed by Hamilton, Barrichello, Button, Massa and Vettel.
01 N. Rosberg Williams 1:15.243 45 laps
02 L. Hamilton McLaren 1:15.445 35 laps
03 R. Barrichello Brawn GP 1:15.590 41 laps
04 J. Button Brawn GP 1:15.774 36 laps
05 F. Massa Ferrari 1:15.832 42 laps
06 S. Vettel Red Bull 1:15.847 33 laps
07 H. Kovalainen McLaren 1:15.984 45 laps
08 K. Räikkönen Ferrari 1:15.985 43 laps
09 K. Nakajima Williams 1:16.260 43 laps
10 N. Piquet jr. Renault 1:16.286 43 laps
11 F. Alonso Renault 1:16.552 39 laps
12 M. Webber Red Bull 1:16.579 27 laps
13 A. Sutil Force India F1 1:16.675 38 laps
14 J. Trulli Toyota 1:16.915 43 laps
15 S. Buemi Scuderia Toro Rosso 1:16.983 48 laps
16 S. Bourdais Scuderia Toro Rosso 1:17.052 48 laps
17 N. Heidfeld BMW 1:17.109 40 laps
18 T. Glock Toyota 1:17.207 45 laps
19 G. Fisichella Force India F1 1:17.504 45 laps
20 R. Kubica BMW no time 2 laps
Source : Planet F1