Lewis Hamilton posted the fastest times during Friday's two practice sessions for the Hungarian Grand Prix, while Michael Schumacher was unhurt after crashing into a wall of tires on the wet track.
Hamilton, who was forced to retire near the end of last week's German Grand Prix — his 100th Formula One race — was far from complacent.
"It's been a real positive day and I'm very, very happy," Hamilton said. "We still got work to do. The Red Bulls look very quick and so do the Lotus and, obviously, Ferrari as well, so we are by no means feeling comfortable."
Hamilton's afternoon time of 1 minute, 21.995 seconds came before the rain, beating Kimi Raikkonen of Lotus by 0.185 seconds. Bruno Senna of Williams was third.
The rain, which started less than an hour into the 90-minute practice, caused seven-time world champion Schumacher to skid and crash.
Schumacher is considered one of the best drivers in wet conditions but had a similar accident in the rain a week ago in practice. After Friday's collision, he appeared unhurt and climbed into a television camera tower to watch the other cars.
"Michael out in the tire wall. All OK... Not his car," the Mercedes team said on Twitter after the crash.
"I just locked up and ran out of road," Schumacher said. "By hitting the tires, I lost the front wing, but other than that, nothing is damaged on the car, I believe. It was the kind of incident that happens when suddenly a shower hits the dry track. The car felt OK until then."
Drivers will have a third practice run on Saturday, one hour on the track ending at noon, before the qualifying session for Sunday's race.
The Hungaroring is one of the slowest tracks on the circuit, with many tight corners and little room for passing.
"Overtaking here is very, very difficult if not almost impossible, so positioning is very important," said Hamilton, who won the Hungarian race in 2007 and 2009.
Hamilton's McLaren teammate, Jenson Button, was sixth in the afternoon practice, one of nine drivers within one second of the leader.
Defending champion Sebastian Vettel of Red Bull was 15th in the morning practice and eighth in the afternoon.
"There's still a lot of room for improvement," said Vettel, who was penalized 20 seconds and demoted to fifth place from second at Hockenheim because of an illegal passing move.
The points lost in Germany could be costly for Vettel, who is 44 points behind the 154 of championship leader Fernando Alonso of Ferrari and 10 back of Red Bull colleague Mark Webber.
Alonso won his first Formula One race in Hungary in 2003 and said it was difficult to predict how the qualifying session would go.
"Because of this afternoon's rain, we did not manage to try the dry tires over a long run, but at least in the morning we managed to complete the work relating to the aerodynamic updates," said Alonso, who, after a poor start to the season, has two victories and a second-place finish in the last three races. "Now it's up to our engineers to do all the analysis and put together the best possible package for the rest of the weekend."
In the morning session, Hamilton had a time of 1:22.821, edging Button by 0.101 seconds. Alonso was third in the morning, more than half a second behind Hamilton.
Temperatures around 91 degrees are forecast for Saturday, and there's also a chance of rain during Sunday's race.
The Hungaroring event is the 11th of 20 races on the 2012 calendar and leads into a monthlong break before the Belgian Grand Prix on Sept. 2.