Massa tops session one
Championship leader Hamilton sixth after opening practice
Ferrari's Felipe Massa recorded the quickest time during the first free practice session ahead of Sunday's Canadian Grand Prix.
The Brazilian clocked a best lap of one minute 17.553 around the 2.71-mile Circuit Gilles Villeneuve, a quarter of a second faster than BMW Sauber's Robert Kubica with Heikki Kovalainen third fastest for McLaren Mercedes.
Nick Heidfeld confirmed BMW Sauber's strong start to the weekend with the fourth fastest time ahead of defending World Champion Kimi Raikkonen.
Current Drivers' Championship leader Lewis Hamilton was sixth-fastest for McLaren, clocking a time of 1:18.303s.
Overnight rain resulted in a wet track on a cool and overcast morning in Montreal as the 90-minute session got underway.
Massa, who was disqualified from last year's race alongside Giancarlo Fisichella after both drivers ignored a pit-lane red light, left it until his final lap to post his best time.
Kubica, who finished second in Monaco behind Hamilton two weeks ago, did likewise.
Raikkonen was almost three-quarters of a second slower than his Ferrari team-mate despite posting the fastest sector one time of the session.
Meanwhile, Hamilton put in the fewest laps of all the drivers, eight, on his return to the circuit at which he claimed his maiden grand prix victory 12 months ago.
Mark Webber was the 'best of the rest' behind the leading three teams, the Red Bull driver clocking 1:18.712s ahead of team-mate David Coulthard.
Kazuki Nakajima of Williams ninth quickest with a lap of 1:18.809s, one place ahead of Renault's Fernando Alonso 10th.
Honda's Jenson Button was the slowest of the 20 drivers, with a best lap of 1:21.542s.
Canadian Grand Prix, Friday practice (session one):
1. Felipe Massa (Brazil) Ferrari 1:17.553
2. Robert Kubica (Poland) BMW Sauber 1:17.809
3. Heikki Kovalainen (Finland) McLaren 1:18.133
4. Nick Heidfeld (Germany) BMW Sauber 1:18.182
5. Kimi Raikkonen (Finland) Ferrari 1:18.292
6. Lewis Hamilton (Britain) McLaren 1:18.303
7. Mark Webber (Australia) Red Bull 1:18.712
8. David Coulthard (Britain) Red Bull 1:18.809
9. Kazuki Nakajima (Japan) Williams 1:18.971
10. Fernando Alonso (Spain) Renault 1:19.005
11. Nico Rosberg (Germany) Williams 1:19.093
12. Sebastian Vettel (Germany) Toro Rosso 1:19.228
13. Timo Glock (Germany) Toyota 1:19.346
14. Jarno Trulli (Italy) Toyota 1:19.568
15. Giancarlo Fisichella (Italy) Force India 1:19.815
16. Adrian Sutil (Germany) Force India 1:19.888
17. Nelson Piquet (Brazil) Renault 1:20.091
18. Rubens Barrichello (Brazil) Honda 1:20.173
19. Sebastien Bourdais (France) Toro Rosso 1:20.541
20. Jenson Button (Britain) Honda 1:21.542