* Pre-race: A change in climatic conditions is announced. Teams are allowed to adjust their cars to suit the damp conditions, if they wish. Minardi drivers Robert Doornbos and Christijan Albers opt to start from the pits rather than 18th and 19th positions. Intermediate tyres are the order of the day.
* Lap 1: Pole-sitter Juan Pablo Montoya makes a clean start to lead Kimi Räikkönen into La Source. Jarno Trulli briefly threatens the Finn, but slots into third. World championship leader Fernando Alonso runs fourth ahead of Michael Schumacher, Takuma Sato (up from 10th), Jenson Button, Ralf Schumacher, Felipe Massa, Mark Webber, David Coulthard, Giancarlo Fisichella (relegated from third to 13th on the grid in the wake of an unscheduled engine change), Christian Klien, Rubens Barrichello, Antonio Pizzonia, Jacques Villeneuve, Tiago Monteiro, Narain Karthikeyan and the Minardis, Doornbos ahead of Albers. Montoya opens up a 1,4s lead.
* Lap 2: Räikkönen cuts his deficit by 0.2s. Coulthard and Fisichella pass Webber.
* Lap 3: Räikkönen closes again: 0.7s. Trulli and the others are drifting slowly.
* Lap 4: Montoya eases away: 1,5s. Albers pits and rejoins.
* Lap 6: Fisichella passes Coulthard for 10th on the run from La Source to Eau Rouge.
* Lap 7: Ralf Schumacher passes Button for seventh; Fisichella makes short work of Massa and moves up to ninth. Doornbos pits and rejoins.
* Lap 9: The gap between the top two stabilises at 1.0s. Trulli is 4.6s further adrift. Ralf Schumacher is harassing Sato. Fisichella pinches eighth from Button. Montoya laps Doornbos.
* Lap 10: Ralf Schumacher makes a scheduled stop.
* Lap 11: Fisichella makes an unscheduled one, against the tyre wall at Raidillon. He hops out but the Safety Car is deployed and everybody bar Villeneuve heads for the pits. While Montoya stops, Räikkönen slows the remainder of the field to avoid being stacked up in the pits. Webber takes a punt on dry-weather tyres.
* Lap 12: Post stops, Montoya leads Villeneuve, Ralf Schumacher, Räikkönen, Alonso, Trulli, Massa, Barrichello, Monteiro, Michael Schumacher, Sato, Klien, Coulthard, Karthikeyan, Webber, Button, Pizzonia, Albers and Doornbos. Michael Schumacher, Sato, Coulthard, Webber, Button and Pizzonia make second stops.
* Lap 13: Trulli and Klien come in again.
* Lap 14: Restart. Villeneuve runs wide at La Source and slips to fourth. Sato rams Michael Schumacher at the same spot and both retire. The German swipes a glove in his assailant’s general direction. The crowd jeers the Japanese driver. Montoya pulls 4.7s out on Ralf Schumacher. Räikkönen is another 2.9s in arrears.
* Lap 15: The order reads: Montoya, Ralf Schumacher, Räikkönen, Villeneuve, Alonso, Massa, Barrichello, Massa, Barrichello, Webber, Monteiro, Button, Coulthard, Pizzonia, Karthikeyan, Trulli, Klien and the lapped Minardis, Albers ahead of Doornbos.
* Lap 16: Ralf Schumacher is reeling the leader in: the gap is down to 2.8s.
* Lap 17: Montoya’s advantage is further shredded: it’s just 1.9s. The yet-to-stop Villeneuve is still ahead of Alonso – by 2.3s – and Monteiro is clinging onto ninth, although Button is right on his tail.
* Lap 18: Button passes Monteiro.
* Lap 19: Coulthard retires from 11th place at La Source, with a plume of smoke visible from his engine bay. Oil is spotted on the track. Ralf Schumacher gets to within 0.7s of Montoya. Räikkönen is half a dozen seconds behind.
* Lap 20: Villeneuve makes his first stop and drops from fourth to eighth, just ahead of Button. Räikkönen edges a couple of tenths nearer the top two. Alonso is all on his own in fourth.
* Lap 21: Montoya stretches his legs a little and pulls 1.1s clear. Albers makes his second stop.
* Lap 23: Doornbos pits.
* Lap 24: Ralf Schumacher pits and gambles on dries. Montoya leads Räikkönen by 6.5s. Button passes Villeneuve for eighth around the outside of Pouhon. Doornbos runs wide onto the grass and pits at the end of the lap.
* Lap 25: Ralf Schumacher spins at Les Combes. Cue another pit stop. The wets go back on. Räikkönen cuts Montoya’s lead by 0.5s.
* Lap 26: Only 4.9 seconds separate the leaders. Webber is challenging Barrichello for fifth. A queue is developing behind Villeneuve: Monteiro, Pizzonia and Karthikeyan are in it.
* Lap 27: Räikkönen closes in again: 4.5s. Monteiro passes Villeneuve.
* Lap 28: Räikkönen is within 2.8s of Montoya. Pizzonia passes Villeneuve.
* Lap 29: Räikkönen laps in 1m55.964s – the race’s fastest yet – and closes to within 2.2s. Massa pits from fourth and rejoins on dry tyres. Villeneuve survives a sideways moment at Eau Rouge, but Karthikeyan passes him as they approach Les Combes. The Indian runs wide and bounds across the grass but stays ahead of his quarry.
* Lap 30: Räikkönen laps in 1m55.848s: the gap is 1.6s. Monteiro pits.
* Lap 31: The McLarens are closer still: 1.1s. Barrichello peels in from fourth. Massa spins at the Bus Stop: dries are not yet the way forward.
* Lap 32: Montoya leads by 0.4s. Alonso, Webber, Karthikeyan and Trulli pit.
* Lap 33: Montoya peels in and rejoins on intermediates. Button and Pizzonia stop, too.
* Lap 34: Räikkönen laps in 1m53.810s. Montoya is second, 26.4s adrift, with Alonso still a solitary third.
* Lap 35: Räikkönen makes his final scheduled stop and rejoins ahead of Montoya. Trulli crashes out of 11th place at Les Combes. Button passes Webber for fifth at the Bus Stop.
* Lap 36: Räikkönen leads Montoya by 6.7s. Alonso is third from Barrichello, Button, Webber, Ralf S, Pizzonia, Villeneuve and Monteiro. Massa, Klien, Karthikeyan, Albers and Doornbos are lapped.
* Lap 37: Klien passes Massa for 11th at La Source.
* Lap 38: Button slices past Barrichello at the Bus Stop to take fourth. Webber pits from sixth and fits dry tyres.
* Lap 39: Klien – 11th and on dry tyres – is lapping faster than almost anyone bar Räikkönen. Pizzonia pits for dries.
* Lap 40: Barrichello and Pizzonia pit for dries.
* Lap 41: Webber sets fastest lap – 1m52.370s. Pizzonia rams Montoya at Les Combes and punts him out of the race. Alonso moves up to second. Ralf Schumacher pits.
* Lap 43: Ralf Schumacher laps in 1m 51.943s.
* Lap 44: Räikkönen wins by 28.3s from Alonso, who needs just six more points to clinch the world title. Button is only 3.4s shy of second place by the end. Webber, Barrichello, Villeneuve and Ralf Schumacher – almost as one across the line – and Monteiro complete the top eight, ahead of Klien, Massa, Karthikeyan, Albers and Doornbos.