Jorge Lorenzo's momentum showed no signs of waning as he topped the opening practice session for his second home race of 2010 at Catalunya.
The Yamaha rider and runaway championship leader swapped the top spot with LCR Honda's Randy de Puniet early on before pulling clear. He was later challenged – and briefly headed by – Casey Stoner, before moving back ahead of the Ducati with a 1m43.4sec, which he later improved to a benchmark 1m43.259sec.
Stoner progressed to a 1m43.631sec with his final run to secure second, ahead of the two Hondas. Dani Pedrosa's last lap got him in front of teammate Andrea Dovizioso for third.
Ben Spies (Tech 3 Yamaha) languished near the foot of the times as he learned the circuit before leaping to fifth right at the end. Pramac Ducati's Aleix Espargaro was a top 10 factor throughout, and ended up an outstanding sixth, pushing de Puniet back to seventh.
It was a quiet session for Nicky Hayden on the second Ducati. As low as 14th for much of the afternoon, he eventually got up to eighth. Colin Edwards (Tech 3 Yamaha) and Marco Simoncelli (Gresini Honda) completed the top 10.
Alvaro Bautista showed Suzuki's best form for several events by holding a top six place at first, before crashing. He was able to walk back to the pits and rejoin, but fell to 12th.
Marco Melandri completed 22 laps as he evaluated his shoulder after dislocating it at Assen a week ago. The Gresini Honda rider was 14th but just 1.5sec off the pace.
Valentino Rossi's substitute Wataru Yoshikawa was unsurprisingly slowest as he acclimatized to his sudden elevation into MotoGP. He was within 4.7sec of the pace, though, after a long battle with fellow stand-in Kousuke Akiyoshi, making another appearance for Interwetten Honda while Hiroshi Aoyama recovers from his Silverstone crash.
Pos Rider Team Time Gap
1. Jorge Lorenzo Yamaha 1m43.259s
2. Casey Stoner Ducati 1m43.412s + 0.153s
3. Dani Pedrosa Honda 1m43.631s + 0.372s
4. Andrea Dovizioso Honda 1m43.725s + 0.466s
5. Ben Spies Tech 3 Yamaha 1m43.854s + 0.595s
6. Aleix Espargaro Pramac Ducati 1m44.136s + 0.877s
7. Randy de Puniet LCR Honda 1m44.196s + 0.937s
8. Nicky Hayden Ducati 1m44.440s + 1.181s
9. Colin Edwards Tech 3 Yamaha 1m44.551s + 1.292s
10. Marco Simoncelli Gresini Honda 1m44.634s + 1.375s
11. Loris Capirossi Suzuki 1m44.641s + 1.382s
12. Alvaro Bautista Suzuki 1m44.692s + 1.433s
13. Mika Kallio Pramac Ducati 1m44.745s + 1.486s
14. Marco Melandri Gresini Honda 1m44.806s + 1.547s
15. Hector Barbera Aspar Ducati 1m45.004s + 1.745s
16. Kousuke Akiyoshi Interwetten Honda 1m47.757s + 4.498s
17. Wataru Yoshikawa Yamaha 1m48.015s + 4.756s