Final positions after 78 laps:
1 F Alonso (Renault)
2 JP Montoya (McLaren)
3 D Coulthard (Red Bull)
4 R Barrichello (Honda)
5 M Schumacher (Ferrari)
6 G Fisichella (Renault)
7 N Heidfeld (Sauber)
Lap 78: Alonso powers to victory, Montoya takes second and Coulthard grabs Red Bull's first podium.
Barrichello holds off former team-mate Michael Schumacher for fourth. Fisichella was sixth with Heidfeld a lap back in seventh.
Lap 76: Alonso leads by 16.8 secs and is cruising, Montoya too. Coulthard is 38 secs back and is being pressured by Barrichello. But the Brazilian is about to fend off Michael Schumacher.
Lap 74: Michael Schumacher is only five seconds behind fourth-placed Barrichello and sets the fastest lap of the race (1:15.1).
Lap 73: Trulli's car packs up coming out of Ste Devote. Coulthard takes third.
Lap 71: The top five hold station but Michael Schumacher is now within 10 seconds of Barrichello.
Lap 68: Michael Schumacher is still lapping in the 1:15s.
Lap 66: Michael Schumacher is 17 seconds behind former team-mate Barrichello.
Lap 64: Alonso leads by 15.8 secs from Montoya with Trulli another 31 secs back in third and Coulthard a further 1.4 back in fourth.
Lap 63: Barrichello is given a drive-through penalty for speeding in the pitlane.
Lap 62: Alonso leads Montoya by 16.6 seconds with Barrichello 24.6 secs back. Michael Schumacher is behind Alonso and is trying to unlap himself.
Lap 60: Michael Schumacher is lapping more than three seconds faster than Coulthard, and has narrowed the gap to fifth to 38.9 secs.
Lap 58: Michael Schumacher is the fastest man on the course. The Ferrari driver is in sixth but 46 seconds behind Coulthard.
Villenueve gets a drive-through penalty for overtaking under the safety car.
Lap 57: Klien pulls out from fifth.
Lap 56: Alonso stretches his lead up to 14 seconds. Lap 54: Alonso leads Montoya by 12 seconds with Barrichello a further seven seconds behind in third.
Trulli, Klien and Coulthard are driving line astern in fourth, fifth and sixth with Michael Schumacher nearly a minute back in seventh.
Lap 52: Rosberg's car hits a barrier and he is out of the race. Everyone up to Coulthard in sixth has been lapped.
Lap 51: The safety car pulls back in at the end of lap 51 and racing begins again. But Montoya in second is five cars behind leader Alonso.
Lap 50: Raikkonen pulls off the track, with his McLaren on fire. Michael Schumacher moves to seventh.
Lap 49: Michael Schumacher moves up to ninth as a result of all the second-stoppers.
Lap 48: The leaders sweep past Klien in seventh. Webber slows and pulls over on the exit from the pit lane. The car is on fire and the safety car is deployed.
Alonso and Raikkonen immediately pit, as do Montoya, Fisichella, Liuzzi and Rosberg.
Lap 46: Michael Schumacher is up to 12th as Villenueve pits. Barrichello and Trulli also stop. Webber has been seriously hampered by backmarkers and is 6.2 seconds behind in third.
Lap 45: Alonso now leads Raikkonen by 1.2 seconds with Webber 1.1 back and Montoya 2.2 adrift. Barrichello is more than 37 seconds behind in fifth.
Lap 43: Klien pits from seventh. Alonso sweeps past Fisichella, while Raikkonen is slowed briefly before also getting past.
Lap 40: Fisichella flies up to 10th with another breathtaking move at the chicane. The leaders have lapped Coulthard in 10th and Alonso is closing on Renault team-mate Fisichella.
Lap 39: Fisichella from 13th gets past Coulthard around the chicane. Ralf Schumacher pits and comes out in 18th.
Lap 38: Everyone up to Jenson Button in 15th has been lapped. The leaders' times are slowing significantly as they encounter heavy traffic.
Lap 37: Michael Schumacher pits from 13th and emerges in 19th. Massa slows third-placed Webber as he steams past. Massa then pits.
Lap 34: Alonso finds some more speed on this lap as he escapes from traffic.
Lap 32: It's a four-horse race now. Barrichello is 28.4 secs back in fifth. Meanwhile, there's a procession from 10th to 15th, with the cars separated by just a few seconds.
Lap 30: Alonso is slowing, lapping in the 1:18s. Montoya in fourth is closing on the three leaders.
Lap 29: Barrichello is still more than 22 seconds behind fourth-placed Montoya. Coulthard pits and exits 12th, just in front of Michael Schumacher.
Lap 27: Fisichella stops, emerging in 14th. Michael Schumacher is up to 14th, 0.5 secs behind Villeneuve.
Lap 26: The race order settles down again after the first round of pit stops for the front runners. Alonso leads by 0.6 secs from Raikkonen, with Webber right on his tail.
Montoya is 98.7 secs behind in fifth with Coulthard and Fisichella close behind in sixth and seventh.
Lap 25: Webber makes his stop and comes back out in third.
Lap 24: Rosberg pits, also in 10.3. Alonso also stops.
Lap 22: Raikkonen pits in 10.3 seconds and exits in third.
Lap 20: Michael Schumacher dives past Button going into the swimming pool complex to reach 15th. Montoya pits but remains fourth with the huge gap back to Barrichello.
Lap 19: Raikkonen again responds to Alonso's surge and sets a fastest lap of 1:15.325 to close to within 0.6 secs of the leader.
Lap 18: Alonso sets another quick lap to open a small gap of 1.1 seconds on Raikkonen. Barrichello in fifth is more than 25 seconds behind.
Lap 17: Albers is handed a drive-through time penalty but as he is in 18th it won't affect the leaders too much.
Lap 16: Webber is closing slightly on the leaders again as the traffic comes into play. The Australian is 2.3 seconds behind Raikkonen.
Lap 14: After slowing to lap backmarker Franck Montagny, Alonso cranks up the pace again.
Lap 13: Michael Schuamcher is making no further headway as he trundles around in 16th behind Jenson Button.
Lap 11: Webber and Montoya lap Monteiro, who has been into the pit for a nose cone change.
Lap 9: Barrichello is now more than 20 seconds adrift.
Lap 8: Alonso sets the first lap in the one minute 15 seconds region (1:15.924) and Raikkonen responds with 1:15.832.
Lap 7: Alonso and Raikkonen are easing away from Webber, with the gap stretching to 1.7 seconds. Barrichello is now 14 seconds adrift of the leader.
Lap 5: The gap between Montoya in fourth and Barrichello in fifth is more than 11 seconds. But there are three drivers massing immediately behind Barrichello.
Lap 4: Raikkonen sets the fastest lap but is 0.447 behind Alonso.
Lap 3: Michael Schumacher is crawling all over the back of Jenson Button in 15th. Webber is dropping back, almost two seconds behind the leading pair.
Lap 2: Raikkonen swoops past Webber coming out of Ste Devote to go second.
Lap 1: From the start, Fernando Alonso gets off quickly as behind him Mark Webber dives across to cover Kimi Raikkonen. Nico Rosberg makes up two places to sixth, Jenson Button drops two from 13th to 15th and Michael Schumacher moves up to 18th after starting from the pit lane.
1255: Michael Schumacher will start from the pit lane after the penalty imposed in qualifying. This does mean he can use as much fuel as he wants.
1245: The grid is a sea of people as drivers, mechanics, officials, media and hangers-on mill about before the start.
1230: Michael Schumacher, smiling and waving, strolls down to the garages surrounded by a phalanx of Ferrari bigwigs such as team boss Jean Todt. A microphone is thrust under his nose but he says nothing and marches on imperiously. Still smiling.
1215: With 45 minutes to go before the start of the race, the sun is shining and the sky is blue as the F1 paddock continues to buzz following the penalty imposed on Michael Schumacher in qualifying.
Schumacher set the fastest time in qualifying but was put to the back of the grid after race officials ruled he had deliberately stopped on the track, preventing his rivals - including title rival Fernando Alonso - from setting a faster time.
World champion Alonso is gunning for his first victory at the Monaco Grand Prix.
The Ferrari driver's punishment gives Alonso a golden opportunity to establish an even more daunting championship lead.
The Spanish Renault driver heads into the race with a 15-point advantage over Schumacher, who faces a tough task to score points on the F1 track where it is most difficult to overtake.
Williams driver Mark Webber lines up alongside Alonso at the front of the grid after an impressive showing in qualifying, but it remains to be seen if his car has the speed or reliability to challenge the Renault.
McLaren drivers Kimi Raikkonen and Juan Pablo Montoya, who line up third and fourth, are expected to mount a tougher challenge to Alonso.
Honda's hopes rest with Rubens Barrichello, who is fifth on the grid, after Jenson Button produced a very disappointing 14th fastest time in qualifying.