Ferrari driver Fernando Alonso has got his campaign at the Belgian Grand Prix off to a positive start by finishing fastest in the first practice.
McLaren's Jenson Button took an early lead, but conditions began to worsen slightly when rain descended upon the track at Spa.
The bottom end of the circuit appeared to remain dry, while the state of the track towards the finish line was damp, making testing that slightly more difficult for the drivers until the latter stages of the practice when the surface began to dry up.
Red Bull's Championship leader Sebastian Vettel felt the effects of the slippery surface by spinning down at turn one, but there was no damage done and he managed to finish sixth in the standings.
Force India's Paul di Resta completed the circuit second-quickest, while his teammate Adrian Sutil finished just behind him.
Lewis Hamilton recorded the 15th-fastest time in his Mercedes.
First practice full standings:
1. Fernando Alonso (Ferrari)
2. Paul di Resta (Force India)
3. Adrian Sutil (Force India)
4. Sergio Perez (McLaren)
5. Nico Rosberg (Mercedes)
6. Sebastian Vettel (Red Bull)
7. Esteban Gutierrez (Sauber)
8. Nico Hulkenberg (Sauber)
9. Daniel Ricciardo (Toro Rosso)
10. Valtteri Bottas (Williams)
11. Felipe Massa (Ferrari)
12. Pastor Maldonado (Williams)
13. Jean-Eric Vergne (Toro Rosso)
14. Jenson Button (McLaren)
15. Lewis Hamilton (Mercedes)
16. Heikki Kovalainen (Caterham)
17. Giedo van der Garde (Caterham)
18. Max Chilton (Marussia)
19. Mark Webber (Red Bull)
20. Jules Bianchi (Marussia)
21. Kimi Raikkonen (Lotus)
22. Romain Grosjean (Lotus)
