Lewis Hamilton led Nico Rosberg in a commanding Mercedes one-two in the opening practice session for Formula 1's Chinese Grand Prix at Shanghai.
Rosberg had been the initial pacesetter on a 1m40.412s, as Hamilton's first lap was spoiled when he locked up and ran off-course at the tight Turn 14 hairpin.
It was Rosberg's turn to go awry on the second outings, though, locking up into Turn 6 and visiting the run-off area.
He managed to improve the benchmark to a 1m39.574s later in that run, but Hamilton outpaced it by half a second as he did a 1m39.033s just after the session's halfway mark.
That lap kept the world champion on top to the flag, although the Mercedes continued to push on heavier fuel in the final part of the session.
In cold and breezy conditions, countless drivers had minor excursions and the Mercedes pair were among the most frequent transgressors, with Hamilton repeating Rosberg's Turn 6 error and later skittering sideways off-track at Turn 1 after losing the back end mid-corner.
When Hamilton established himself on top, the Mercedes were nearly two and a half seconds clear of the rest of the field.
That margin came down, but even Malaysian GP winner Sebastian Vettel's best lap for Ferrari was still 1.1s off the pace as he took third.
That lap came in the final seconds of the session, and until that point Vettel had looked set to end up 1.5s down on the leader.
Three Ferrari-powered cars chased the Mercedes, with Kimi Raikkonen slotting in behind team-mate Vettel and Felipe Nasr making a late jump to fifth for Sauber.
Renault's best cars were sixth to eighth - Red Bull duo Daniel Ricciardo and Daniil Kvyat leading Toro Rosso man Carlos Sainz Jr, who swiftly escaped a spin at Turn 1 in the first part of the session.
The Williams of Valtteri Bottas and Felipe Massa completed the top 10, despite Massa spinning down the run-off at the hairpin on a late run.
Pastor Maldonado spent a long spell in third for Lotus before falling back to 11th.
His team-mate Romain Grosjean stood aside to let GP2 champion and Lotus test driver Jolyon Palmer make his debut in a grand prix practice session.
Palmer had an early spin and was 15th, 0.6s off Maldonado.
Jenson Button was the quicker of the McLarens in 13th, while the Manor-run Marussias trailed the field but had a trouble-free session.
PRACTICE ONE RESULTS:
|6||Daniel Ricciardo||Red Bull/Renault||1m41.029s||1.996s||21|
|7||Daniil Kvyat||Red Bull/Renault||1m41.097s||2.064s||24|
|8||Carlos Sainz Jr.||Toro Rosso/Renault||1m41.112s||2.079s||23|
|12||Max Verstappen||Toro Rosso/Renault||1m41.575s||2.542s||28|
|16||Sergio Perez||Force India/Mercedes||1m42.141s||3.108s||22|
|18||Nico Hulkenberg||Force India/Mercedes||1m42.184s||3.151s||19|