Lewis Hamilton topped the times in a rain-interrupted session as the 2016 Formula 1 season got under way with first Australian Grand Prix practice at Melbourne's Albert Park.
The reigning world champion clocked a 1m29s.725s for Mercedes, 0.421 seconds quicker than Red Bull's Danill Kvyat with Daniel Ricciardo seven tenths adrift in third.
Rain earlier in the morning soaked the track and though a dry line appeared, the session was disjointed as showers fell intermittently throughout.
Drivers were limited to a 15-minute window towards the end of the a 90-minute session to get some representative dry running in.
A heavy shower hit with a few minutes to go, catching out Kimi Raikkonen and Ricciardo, with the Red Bull getting stuck deep in the gravel.
Nico Hulkenberg was one of the few drivers to get a lap in on the softs and ended up fourth quickest ahead of Max Verstappen, who spun his Toro Rosso at Turn 5 in the damp conditions.
Nico Rosberg did not manage to set a lap time when the track was at its driest, but did get some soft tyre running in late on to finish sixth.
McLaren drivers Fernando Alonso and Jenson Button were tasked with working to complete the team's final configuration and set-up work as it had failed to complete its testing programme.
The duo completed 27 laps between them to finish seventh and eighth quickest respectively.
Force India's Sergio Perez and Kevin Magnussen in the Renault completed the top 10.
Newcomer Haas limited its running given the conditions and its lack of spare parts with Romain Grosjean and Esteban Gutierrez completing just 14 laps between them.
Sebastian Vettel and Carlos Sainz Jr were the only drivers not to set a time.
Vettel completed eight installation laps while Sainz managed just three after spending most of the session in the Toro Rosso garage having stopped at the pitlane entry early on.
PRACTICE ONE TIMES
|2||Daniil Kvyat||Red Bull/Renault||1m30.146s||0.421s||14|
|3||Daniel Ricciardo||Red Bull/Renault||1m30.875s||1.150s||13|
|4||Nico Hulkenberg||Force India/Mercedes||1m31.325s||1.600s||8|
|5||Max Verstappen||Toro Rosso/Ferrari||1m31.720s||1.995s||14|
|9||Sergio Perez||Force India/Mercedes||1m33.370s||3.645s||6|
|22||Carlos Sainz Jr.||Toro Rosso/Ferrari||-||-||3|