Rubens Barrichello may have posted the fastest time of the opening free practice session in Monaco, but there were some ominous names lining up to be his chief opposition during the 90 minutes.

The Brazilian, despite suffering one of the few off-track moments of the session, left the opening benchmark of the weekend at 1min 17.189secs, but had Formula One's big two teams in his wake as the chequered flag came down, with McLaren and Ferrari both having taken rare turns at the top of the timesheets. Barrichello's margin at the end was three-tenths of a second, but Felipe Massa, Lewis Hamilton, Heikki Kovalainen and Kimi Raikkonen filled the next four places as the unpredictability of Monaco allowed the hitherto labouring giants a moment of optimism.

While times were up on those in the record books, primarily as the majority opted to remain on the harder of Bridgestone's two chosen options, Barrichello worked his way down into the 1min 17s to deny Massa top spot, while Hamilton, who wound up just 0.079secs shy of the Ferrari man, had sat atop the list for some time mid-session.

Kovalainen and countryman Raikkonen were not quite so flamboyant, although the McLaren man was among the first and few to try the softer tyre option - and joined Barrichello in taking to the Ste Devote escape road. Other than their indiscretions, however, there was no embarrassment for anyone, save for the Renault engine department as Sebastian Vettel's unit let go mid-session.

Behind Raikkonen, who was 0.650secs slower than Barrichello, Williams duo Kazuki Nakajima and Nico Rosberg filled sixth and seventh spots, ahead of championship leader Jenson Button, Fernando Alonso and Mark Webber, although the Australian also reported something amiss at the rear of his Red Bull.

Another Red Bull-backed machine topped the times early on, as Sebastien Buemi pushed Toro Rosso to the fore before many had decided that track conditions were conducive to anything more than systems checks. The Swiss eventually wound up just missing a spot in the top half of the order, and sitting ahead of Nelson Piquet Jr, Vettel, team-mate Sebastien Bourdais and Force India's Giancarlo Fisichella.

The Italian veteran got the better of some more illustrious teams with both BMW Saubers and the two Toyotas sandwiching the second FIF1 car of Adrian Sutil in the bottom five after reporting handling woes for much of the session.