Ahead of today's first free practice session the air temperature is 23 degrees C, while the track temperature is 30 degrees.
Today we will see 22 drivers in action, the 18 drivers due to take part in Sunday's race, plus the four 'third drivers' for McLaren, Red Bull, Jordan and Toyota. BAR, of course, is serving the second of its two-race ban.
At 11:00 precisely, the pitlane lights go green and Christijan Albers heads out on to the 'circuit', followed by Klien, Doornbos, Wurz and Friesacher. Karthikeyan, Villeneuve, Massa and Ralf Schumacher, are other drivers keen to explore the condition of the Principality's streets
Five minutes into the session, with the others having returned to their garages following their installation lap, Michael Schumacher takes to the track. The German is shadowed by Raikkonen, Zonta, Barrichello and Fisichella.
With nine minutes gone, and as Juan Pablo Montoya begins his installation lap, Alex Wurz returns to the track to (hopefully) post the first time of the weekend.
As the Red Bull duo of Coulthard and Liuzzi begins their installation laps, Wurz crosses the line to post 1:24.835. Next time around, the Austrian crosses the line at 1:23.171, as Zonta begins his first timed lap.
The McLaren third driver improves to 1:21.171, as Klien posts 1:23.868 and Zonta, 1:26.568.
As Doornbos posts 1:33.177, World Championship leader, Fernando Alonso, begins his installation lap.
Klien improves with a 1:21.117, to go quickest, and then posts 1:20.562, to further consolidate his position at the top of the timesheets. Don't forget, this weekend, Red Bull has 'The Force', courtesy of Star Wars.
Doornbos improves to 1:27.106, which puts him ahead of Friesacher, Karthikeyan, Albers and Monteiro.
Moments later, Friesacher makes it an Austrian 1-2-4, as he posts a 1:25.762, though he is soon leapfrogged by Villeneuve who posts 1:25.729.
Approaching half-time, and with only ten names on the timesheet, Klien is quickest, ahead of Wurz, Liuzzi, Zonta, Villeneuve and Friesacher.
Raikkonen is the first of the 'big guns' to post a time, the Finn goes fourth with a 1:22.196, as Wurz goes quickest with a 1:20.244. Meanwhile, Barrichello is back on track, while Webber begins his installation lap.
As Wurz posts 1:19.601, Villeneuve goes fourth (21.875), ahead of Raikkonen, Friesacher and Karthikeyan.
The Finn improves (21.895), as Webber posts a 1:22.840, to go seventh. Meanwhile, Michael Schumacher is back on track.
On his very first lap, the German goes quickest, posting 1:19.522, however, moments later both Raikkonen and Webber have gone quicker. Ralf goes fifth (19.898) as Barrichello goes ninth.
Klien isn't done however, and posts 1:18.317 to reclaim the top spot. Behind him the action is frantic, with Ralf taking third only to be edged out moments later by Coulthard (19.234).
Michael isn't finished, and bangs in a 1:18.284, then a 18.149, as Alonso goes third (18.936) ahead of Coulthard (18.967).
This is typical Monaco, frenetic.
As Alonso consolidates third (18.493), Montoya, on his first lap, posts a 1:19.552, to go ninth. Elsewhere, Massa goes fourteenth, ahead of Liuzzi, Villeneuve and Trulli.
Trulli improves, but remains at the wrong end of the timesheet, as Fisichella goes sixth.
With seventeen minutes remaining, it's; Michael ahead of Klien, Alonso, Montoya, Coulthard, Fisichella, Raikkonen, Ralf, Webber and Trulli.
Klien is on another hot lap, the Austrian, and the Red Bull looking good this morning. He takes the top spot with a 1:17.511, but fractions of a seconds later he's leapfrogged by Alonso, who crosses the line at 1:17.301.
Michael Schumacher is bumped down to fourth by Alexander Wurz, who crosses the line at 1:18.059.
With thirteen minutes remaining just three drivers are on track - Wurz, Villeneuve and Doornbos - as their rivals prepare for the final onslaught.
The 'climax' begins, first out is Montoya, followed by Fisichella, Ralf, Webber and Barrichello.
The Australian improves to fifth with a 1:18.244, while his teammate improves to eighth (18.859).
Montoya is on a hot lap, the Colombian going quickest in the second sector. He's quickest in the final sector too, crossing the line at 1:17.585 to go third.
Villeneuve improves to fifteenth (20.116) as Barrichello improves to eleventh (19.065). Teammate Michael Schumacher however, goes quickest in the first sector, however he loses ground in the second, the track being very busy. He fails to improve, and remains fourth.
Next time around he's quickest (again) in the first sector, as Montoya goes consolidates his third position with a 1:17.537. Schumacher improves (17.640) but remains fourth, which suggests that he is 'trying something' in the first sector, a tactic he's used in the past at various tracks, concentrating on one particular section of the track.
In the final moments, Montoya bangs in a 1:17.152, to go quickest by 0.179s.
The session ends with the Colombian quickest, ahead of, Alonso, Klien, Michael, Fisichella, Wurz, Webber, Ralf, Coulthard and Barrichello.
Heidfeld is eleventh, ahead of, Raikkonen, Trulli, Villeneuve, Liuzzi, Massa, Zonta, Doornbos, Monteiro, Karthikeyan and Albers.