Paul di Resta set the quickest time during first practice for the Canadian Grand Prix.
The Force India driver's time of 1:21.020 was set on the medium compound tyres towards the end of the 90 minute session.
Most of the session took place in wet conditions, following heavy overnight rain in Montreal.
The wet weather meant that drivers were unable to test Pirelli's development tyres until the circuit dried sufficiently for slicks with 15 minutes remaining.
Nico Rosberg led the way early on until Sebastian Vettel took top spot. As the circuit dried, the times tumbled but Pastor Maldonado still fell foul of the tricky conditions as he suffered a small accident at Turn 4.
The Venezuelan driver lost the back end of his Williams FW35 and hit the wall head on, damaging his front wing.
Behind di Resta was fellow Brit Jenson Button, with Romain Grosjean in third and Fernando Alonso in fourth.
Kimi Raikkonen set the fifth fastest time, ahead of Daniel Ricciardo, Rosberg and Sergio Perez.
Alexander Rossi set the twentieth fastest time as he made his first practice run for Caterham since last year's Spanish Grand Prix.
Jules Bianchi's session ended prematurely when he ran wide at Turn 3 and switched off the engine to prevent damage.