Rosberg heads second Monaco practice

Rubens Barrichello, who had been quickest in the morning, took third this time, ahead of his championship-leading Brawn team-mate Jenson Button, and Felipe Massa in the best of the Ferraris.

McLaren held the advantage for much of the session, with first Heikki Kovalainen then Hamilton establishing themselves at the top following a frenetic opening 20 minutes as countless drivers swapped first place on an ever-improving track.

It was Massa who deposed Hamilton with a soft tyre run just before the one-hour mark, despite getting sideways out of Mirabeau, but he only led the way briefly before Barrichello regained the superiority he had shown this morning with a lap of 1m15.590s, half a second clear of the Ferrari.

Then, when as the pace increased further in the final five minutes, Rosberg and Hamilton thrust themselves to the front. The Williams was first to lead the session, before Hamilton beat it by 0.001s.

Rosberg retaliated though, lapping in 1m15.243s to out-pace Hamilton by 0.202s and give himself opening day bragging rights yet again. A further attempt to improve ended in the Mirabeau escape road, but it did not matter by then.

With Hamilton and Barrichello hanging on to second and third, Button eventually moved up to fourth ahead of Massa after a relatively quiet session.

Red Bull recovered from its troubled morning - which saw Sebastian Vettel stop with a blown engine and Mark Webber lose time with a transmission glitch - to take sixth with Vettel, although Webber was only 12th.

Kovalainen fell back to seventh by the end of the afternoon, followed by Kimi Raikkonen (Ferrari), Kazuki Nakajima in the second Williams, and Renault's Nelson Piquet.

Robert Kubica's involvement in the session was extremely brief. His BMW's engine erupted in a cloud of smoke and flames as he accelerated out of Sainte Devote on what should have been his first flying lap, leaving him stranded at the top of the hill and at the bottom of the timing screens.

That was the most dramatic incident in a session that again saw everyone avoid the barriers, although Massa, Vettel, Sebastien Bourdais and Adrian Sutil visited the Sainte Devote escape road and many others took the shortcut across the chicane.

Pos  Driver       Team                       Time              Laps
 1.  Rosberg      Williams-Toyota       (B)  1:15.243            45
 2.  Hamilton     McLaren-Mercedes      (B)  1:15.445  + 0.202   34
 3.  Barrichello  Brawn-Mercedes        (B)  1:15.590  + 0.347   40
 4.  Button       Brawn-Mercedes        (B)  1:15.774  + 0.531   35
 5.  Massa        Ferrari               (B)  1:15.832  + 0.589   41
 6.  Vettel       Red Bull-Renault      (B)  1:15.847  + 0.604   33
 7.  Kovalainen   McLaren-Mercedes      (B)  1:15.984  + 0.741   44
 8.  Raikkonen    Ferrari               (B)  1:15.985  + 0.742   42
 9.  Nakajima     Williams-Toyota       (B)  1:16.260  + 1.017   42
10.  Piquet       Renault               (B)  1:16.286  + 1.043   42
11.  Alonso       Renault               (B)  1:16.552  + 1.309   38
12.  Webber       Red Bull-Renault      (B)  1:16.579  + 1.336   27
13.  Sutil        Force India-Mercedes  (B)  1:16.675  + 1.432   37
14.  Trulli       Toyota                (B)  1:16.915  + 1.672   42
15.  Buemi        Toro Rosso-Ferrari    (B)  1:16.983  + 1.740   47
16.  Bourdais     Toro Rosso-Ferrari    (B)  1:17.052  + 1.809   47
17.  Heidfeld     BMW-Sauber            (B)  1:17.109  + 1.866   39
18.  Glock        Toyota                (B)  1:17.207  + 1.964   44
19.  Fisichella   Force India-Mercedes  (B)  1:17.504  + 2.261   44
20.  Kubica       BMW-Sauber            (B)  No time              2

All Timing Unofficial