Red Bull's Sebastian Vettel was in imperious form as he took pole position for the Monaco Grand Prix.
The world champion bettered McLaren's Jenson Button by 0.441 seconds with Vettel's team-mate Mark Webber third.
Fernando Alonso was fourth for Ferrari but Lewis Hamilton had a difficult session, finishing seventh fastest but then being demoted to ninth.
The session was re-started after Sauber's Sergio Perez suffered concussion in a heavy crash.
The Mexican has said he wants to race but doctors will not allow him to, following normal F1 practice when a driver suffers concussion.
Monaco's low-speed street circuit demands different qualities from a car than other tracks, but Vettel was still a class apart as he claimed his fifth pole position in six races this season.
Vettel comfortably set his time of one minute 13.556 seconds just before Perez's accident halted the session.
But when the remaining nine cars returned to the track more than half an hour later, no-one was able to reel in the defending world champion.
Hamilton went seventh fastest but was subsequently penalised two places for cutting the chicane during final qualifying.
In the early part of the top-10 shootout, Hamilton vented his frustration when he found himself behind Ferrari's Felipe Massa on his first attempt at a flying and raised his hand at the Brazilian.
After qualifying, the Englishman was clearly unhappy, both with Massa and with the McLaren team strategy.
"I had the pace to be on pole, no doubt about that," said Hamilton.
"Lewis is inevitably frustrated," said McLaren team principal Martin Whitmarsh. "So are we. Lewis was very quick in Q1 and Q2 and really thought he was going to take pole here. If anyone can recover, Lewis can, and I'm sure he will be very motivated to show what he can do."
In contrast, Button, who won in Monte Carlo two years ago, delivered his lap of the weekend just at the right time to reach the front row of the grid.
Vettel said: "Obviously we had a good run which put us on pole but for sure there is a shadow over the last qualifying session with the accident Sergio Perez had.
"We were all waiting and I was asking if we can get an update. Hopefully he is racing soon. It is hard to retain your focus.
"[At the restart] the circuit was a bit more slippery. It was impossible to really improve but it was even more important that we had a solid first run.
"I was very happy. It is very difficult to get everything into one lap. It is easy to make a mistake. You have to be very careful but you have to take risks if you want the lap time.
"We have gained eight metres for Sunday. We will have to wait and see what happens."
Alonso joins Webber on the second row of the grid but the Spaniard, who led much of the last race in Spain before being overhauled in the pits, believes strategy will again be key to the race.
"Maybe we were a little bit quicker than we showed," said Alonso. "The end of Q3 was never a good moment as the track was not in good shape and we lost a couple of tenths.
"The pit lane will decide [on Sunday] as it is extremely difficult to overtake here."
Three accidents on Saturday showed just how close to the edge the drivers are around the narrow, twisting streets of Monte Carlo.
Rosberg had a heavy crash on the exit of the tunnel in final practice but just managed to stop his Mercedes hurtling headlong into the barriers.
The 25-year-old held his nerve well to qualify eighth fastest, even though he was out-qualified for the first time this season by his team-mate Michael Schumacher, who was fifth fastest.
At the end of that session, Vitantonio Liuzzi slid into the barriers coming out of Sainte Devote, the first corner, and crumpled both the front and rear of the car.
There was a more frightening impact to come in qualifying when Perez crashed heavily into the tyre wall at the Nouvelle Chicane with five minutes to go.
It took a long time to extract Perez, who has made a promising start in his rookie season, from the car but he was reportedly conscious before he was taken to the medical centre.
"It was a big impact," commented BBC F1 pundit Eddie Jordan. "It is not easy coming out of the corner. He must have got it wrong and then had no chance of getting away from this."
Venezuelan rookie Pastor Maldonado qualified ninth fastest, two places ahead of his Williams team-mate Rubens Barrichello.
Jaime Alguersuari's Toro Rosso had a troublesome session as he finished 20th below both Team Lotus cars but ahead of the Virgins and Hispanias.
Liuzzi did not take part in qualifying after he crashed his Hispania coming out of Ste Devote in final practice.
His team-mate Narain Karthikeyan also failed to emerge because of a rear suspension failure.
But both men have been allowed to race despite contravening the 107% qualifying rule.
The regulation says cars who fail to set a time that is within 107% of the leading time Q1 will not be allowed to join the grid on race day unless there are extenuating circumstances.
The stewards based their decision on the Hispania drivers' times in final practice, when they were within 107% of the pace-setting Alonso.