Michael Schumacher was fastest in a wet first practice session in Korea.
The Mercedes driver set the quickest time right at the end of the 90 minutes as the track dried out.
With rain still falling at the track as the pitlane exit light turned green, the cars took to the circuit on full wet weather tyres for their installation laps.
After that almost no-one took to the track in the first half of the session, Lewis Hamilton being the exception, doing some exploratory runs in his McLaren.
The track finally started to come to life with half an hour to go. Hamilton was the first to set a time, followed by Sebastien Buemi who headed the times in his Toro Rosso with a lap of 2’03.182.
Buemi’s time remained the fastest until it was beaten by Adrian Sutil with just over a minute remaining.
Schumacher beat his time by three-tenths of a second despite a few off-track moments earlier in his run. He went off again as he turned into the pit lane at the end of his run.
Sutil was poised to improve again but caught up to an HRT during his final run, losing time.
Sebastian Vettel went second fastest despite a spin and another scare when he almost ran into one of the Virgin cars.
Paul di Resta went third quicket on his final run, putting him ahead of Sutil and Buemi.
Jean-Eric Vergne was 13th in his first F1 practice session for Toro Rosso.
Six drivers opted not to set a time including both Ferrari drivers and Jenson Button.
2011 Korean Grand Prix