Mercedes' Nico Rosberg finished on top after the opening practice for the 2013 Formula 1 Monaco Grand Prix. The German, who is bidding for a third consecutive pole position this season, began with a strong 1:16.195 in the morning period.
Ferrari driver Fernando Alonso, still flying after an utterly dominant weekend at the last race, at the Circuit de Cataluña in Spain, was second, with an equally impressive 1:16.282, to finish only 0.087s off the Mercedes' man.
Alonso's team mate, Felipe Massa of Brazil, was third until the final few laps of the session but was deposed by flying Frenchman Romain Grosjean. The Lotus-Renault driver posted 1:16.380 to edge ahead of Massa's 1:16.394, in a thrilling end to the 90-minute session.
The Red Bull Racings of defending world champion Sebastian Vettel and Mark Webber were once again missing from the sharp end of the grid. The Milton Keynes outfit have made a habit of starting weekends slowly and do not usually show their true pace until the second session. So expect Vettel and his team mate to storm up the order in the afternoon.
For information on where and how to watch the second free practice session of the 2013 Formula 1 Monaco Grand Prix, click here.
Vettel's best was a poor 1:17.380 for 10th and he was outpaced his team mate. The Australian managed 1:17.020 for seventh.
Rosberg's team mate, 2008 world champion Lewis Hamilton locked out the front row in Spain two weeks ago but, on present form, the former McLaren ace will struggle. Hamilton managed 1:16.469 for fifth. The gap to his team mate is only 0.274s but with both Ferraris in fine form, the Lotus-Renault thereabouts as well and the Red Bulls yet to show their hand, he needs to improve.
Williams' Pastor Maldonado closed a good session with 1:16.993 for sixth and Hamilton's former team mate, Jenson Button of McLaren should be reasonably happy with 1:17.129 for eight. Button's team mate, Sergio Perez, finished ninth with 1:17.378.
The Woking team are used to running at the sharpest end of the grid but have struggled all season long; they will hope the Honda engines, due in 2015, will improve their long-term fortunes.
The Force India team, with Adrian Sutil and Paul di Resta were expected to perform better than they did in the morning. The latter posted their best time - 1:17.548 for 12th. Sutil was 0.077s and one place behind.
Everybody ran Pirelli's soft tyre compound (P Zero Yellow), with the drivers opting to save the supersoft compounds (P Zero Red) for the second session or maybe qualifying.
As expected, the weather stayed cooperative and sunny, with track temperatures touching 30C and absolutely no rain. Conditions are expected to be largely similar for the second practice session, which starts at 2pm local time (1pm BST).