The 22-year-old championship leader, 12 points clear of double world champion team mate Fernando Alonso after nine races, lapped in one minute 32.515 seconds on an overcast morning.
Ferrari's Kimi Raikkonen, chasing his third win in a row on Sunday, was second on the timesheets and 0.236 seconds slower.
Alonso was third, with the BMW Saubers of Nick Heidfeld and Robert Kubica fourth and fifth. Brazilian Felipe Massa was sixth for Ferrari.
Hamilton had told reporters that he was on the mend after a feverish weekend following his home British Grand Prix and he was top of the timesheets for most of the first 90 minute session.
"I am a bit under weather and I've been ill since Sunday," he had said on Thursday. "But it's much better than it was at the weekend when I had a vicious throat, chesty cough and a bad cold."
The British rookie, whose debut season has produced a string of extraordinary results, can become only the third driver to notch up 10 podium finishes in a row on Sunday.
Champions Renault failed to shine, with Finland's Heikki Kovalainen and Italian Giancarlo Fisichella 18th and 19th respectively.
Germany's Markus Winkelhock also had a difficult start to his first weekend as a full Formula One race driver, clocking the slowest lap of the session in his Ferrari-powered Spyker. He was 4.6 seconds off Hamilton's pace.
Winkelhock, son of late Formula One driver Manfred, is taking over from Christijan Albers for Sunday's race after the team ended the Dutchman's contract over non-payment of sponsorship money.
Spyker have yet to confirm a long-term replacement.
