Fernando Alonso headed the field for Ferrari as two heavy crashes interrupted final practice for the Monaco Grand Prix.
Alonso was half a second faster than Jenson Button's McLaren with Red Bull's Sebastian Vettel fourth.
Both Mercedes and Hispania face fast repairs in their garages after Nico Rosberg and Vitantonio Liuzzi crashed.
The interruptions proved costly for the top teams trying to finetune their form ahead of qualifying at 1300 BST.
The winding streets of Monaco are regarded as the toughest challenge in Formula 1, with driving precision vital to success.
After a day out of the cockpit on Friday, the drivers had to get back into the groove but that did not come so easily to Rosberg.
The German, who lives in the principality, had a frightening crash on the exit of the tunnel but just managed to stop his Mercedes hurtling headlong into the barriers.
The incident left plenty of debris on the track and a valuable 14 minutes of running was lost while it was swept away.
"Rosberg lost the rear," explained 5 live analyst Anthony Davidson. "It's very bumpy there and the car always bottoms out.
"That could have been an almighty shunt and he's very lucky indeed."
Mercedes explained over the pit-to-car radio to Schumacher that Rosberg had "very low rear tyre pressures which probably contributed to the problem".
Rosberg was seen heaving a sigh as he walked back into the Mercedes garage and the team now face a major repair job to get the car ready for qualifying.
Hispania are faced with a similar task after Liuzzi crashed his car with five minutes left on the clock.
The Italian slid into the barriers coming out of Sainte Devote, the first corner, and crumpled both the front and rear of the car.
"I think Mercedes have a better chance of making qualifying than Hispania," commented Davidson.
The two incidents also provided headaches for the leading teams as they tried to assess their form ahead of what is expected to be a tight qualifying session.
Neither Vettel nor his Red Bull team-mate Mark Webber, who was just over a second shy of Alonso's leading time, were able to run a lap on the supersoft tyres which the teams will use to set their fastest laps.
Hamilton, another former winner in Monaco, was also unable to complete a flying lap on the supersoft tyres, although that does not mean he has a set in hand for qualifying as he did do some laps on them.