Lewis Hamilton set the pace in first practice for the Canadian GP as the world champion headed a Mercedes one-two at the top of the timesheets.
Hamilton's benchmark lap of 1:14.755 was three tenths quicker than the best of team-mate Nico Rosberg and only fractionally shy of his pole position time last year.
Hamilton's lap was set on supersofts while Rosberg's personal best was on the ultrasofts.
The session - marking the start of F1's hectic summer schedule which features six races in eight weeks - was briefly red-flagged when Felipe Massa lost control of his Williams into the first corner. The Brazilian was unhurt but the impact was sufficiently violent to rip apart the rear of his FW38 car and bring proceedings to a halt for 10 minutes while the Circuit Gilles Villeneuve barriers were repaired.
Williams later reported that the crash was caused by a fault with the DRS flap on Massa's car staying open as he hurtled along the pit-straight.
Sebastian Vettel was third fastest with Max Verstappen just ahead of Kimi Raikkonen in the second Ferrari.
Verstappen's time was recorded on soft tyres - the slowest but most durable of the three available to the field this weekend. The Red Bull driver was, however, handed a reprimand by the stewards after holding up Valtteri Bottas into the final corner while on a warm-up lap.
Daniel Ricciardo failed to set a representative time as the Red Bull team experimented with different set-ups on their cars.
McLaren's engine providers Honda have introduced a new turbo for the team's cars this weekend. However, Jenson Button endured a frustrating morning with the former world champion restricted to just a handful of laps after his car overheated with smoke billowing out of his MP4-31 at one stage. Team-mate Fernando Alonso was 10th.
Second practice begins at 7pm UK Time.
Practice One timesheet
1. Lewis Hamilton, Mercedes, 1:14.755
2. Nico Rosberg, Mercedes, 1:15.086
3. Sebastian Vettel, Ferrari, 1:15.243
4. Max Verstappen, Red Bull, 1:15.533
5. Kimi Raikkonen, Ferrari, 1:15.618
6. Valtteri Bottas, Williams, 1:16.301
7. Nico Hulkenberg, Force India, 1:16.464
8. Carlos Sainz, Toro Rosso, 1:16.543
9. Sergio Perez, Force India, 1:16.577
10. Fernando Alonso, McLaren, 1:16.633
11. Daniel Ricciardo, Red Bull, 1:16.743
12. Jenson Button, McLaren, 1:16.788
13. Romain Grosjean, Haas, 1:17.008
14. Felipe Massa, Williams, 1:17.065
15. Daniil Kvyat, Toro Rosso, 1:17.310
16. Esteban Gutierrez, Haas, 1:17.319
17. Felipe Nasr, Sauber, 1:17.855
18. Rio Haryanto, Manor, 1:18.103
19. Marcus Ericsson, Sauber, 1:18.129
20. Kevin Magnussen, Renault, 1:18.409
21. Pascal Wehrlein, Manor, 1:18.453
22. Jolyon Palmer, Renault, 1:18.583
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