Defending triple world champion German Sebastian Vettel topped the times as Red Bull delivered a top-two lockout in Friday's opening free practice for Sunday's Hungarian Grand Prix.
On a sweltering day at the Hungaroring circuit north of the capital, Vettel delivered a trouble-free best lap in one minute and 22.723 seconds to outpace team-mate Australian Mark Webber by two-tenths of a second.
Finn Kimi Raikkonen of Lotus was third fastest despite picking up a slow puncture in the closing stages and Spaniard Fernando Alonso of Ferrari fourth ahead of Frenchman Romain Grosjean in the second Lotus.
Briton Jenson Button was sixth fastest for McLaren ahead of German Adrian Sutil of Force India and compatriot Nico Rosberg in the leading Mercedes, Mexican Sergio Perez in the second McLaren and Venezuelan Pastor Maldonado of Williams. The top nine were separated by less than a second.
Briton Lewis Hamilton struggled in his Mercedes as he tested the new Pirelli tyres for the first time - the team having been banned from the Silverstone test last week - and he wound up down in 13th place.
Alonso's Ferrari team-mate Brazilian Felipe Massa was 15th.
On a morning of searing heat at the Hungaroring, the air temperature rose into the low thirties while the track temperature was 43 degrees Celsius - four hours ahead of the second session in the afternoon when overwhelming heat has been forecast.
Rosberg set the first fastest lap of the session in his Mercedes before being outpaced by Perez, Raikkonen, Alonso and then Webber until Vettel pipped him in the closing minutes to deliver a Red Bull double top.