Manama, Bahrain - Lewis Hamilton picked up where he left off by leading Nico Rosberg in a Mercedes one-two in first practice for the Bahrain Formula One Grand Prix on Friday.
The 2008 world champion, winner in steamy Malaysia last weekend ahead of championship leader Rosberg, completed 14 laps and was fastest around the Sakhir circuit with a best time of 1m37.502.
Rosberg's time, on an day where the track temperature hovered around 33 degrees on a bright and breezy afternoon, was 0.231sec slower.
Ferrari's Fernando Alonso was third fastest ahead of Nico Hulkenberg for Force India and McLaren's Jenson Button, the 2009 world champion who will be starting his 250th race on Sunday.
The timesheets reinforced Mercedes' early-season superiority, with four cars powered by their engines in the top five.
Red Bull's quadruple world champion Sebastian Vettel was 10th fastest, with Australian team mate Daniel Ricciardo languishing in 14th, more than a second back.
Alonso, who has finished fourth in both races so far this season, provided some amusement when Ferrari accidentally sent him out with one soft tyre and three mediums on his car. The Spaniard stopped in the pit lane and was pushed back.
Three reserve drivers made debut appearances for the season, with Brazilian Felipe Nasr given track time at Williams, Dutchman Giedo van der Garde at Sauber and compatriot Robin Frijns at Caterham.
Second practice will be cooler and held under the newly-installed floodlights, with the race celebrating its 10th anniversary by switching from an afternoon to day-to-night format for the first time.
1 Lewis Hamilton (Britain) Mercedes - 1m37.502
2 Nico Rosberg (Germany) Mercedes - 1:37.733
3 Fernando Alonso (Spain) Ferrari - 1:37.953
4 Nico Hulkenberg (Germany) Force India - 1:38.122
5 Jenson Button (Britain) McLaren - 1:38.636
6 Kimi Raikkonen (Finland) Ferrari - 1:38.783
7 Kevin Magnussen (Denmark) McLaren - 1:38.949
8 Daniil Kvyat (Russia) Toro Rosso - 1:39.056
9 Sergio Perez (Mexico) Force India - 1:39.102
10 Sebastian Vettel (Germany) Red Bull - 1:39.389
11 Felipe Massa (Brazil) Williams - 1:39.533
12 Jean-Eric Vergne (France) Toro Rosso - 1:39.862
13 Felipe Nasr (Brazil) Williams - 1:40.078
14 Daniel Ricciardo (Australia) RedBull - 1:40.406
15 Adrian Sutil (Germany) Sauber - 1:40.652
16 Pastor Maldonado (Venezuela) Lotus - 1:40.793
17 Jules Bianchi (France) Marussia - 1:40.889
18 Giedo van der Garde (Netherlands) Sauber - 1:40.913
19 Romain Grosjean (France) Lotus - 1:41.036
20 Max Chilton (Britain) Marussia - 1:41.794
21 Robin Frijns (Netherlands) Caterham - 1:42.417
22 Marcus Ericsson (Sweden) Caterham - 1:42.711