Pedrosa looked like he would be the man to beat as he very quickly got to within a few tenths of lap record pace on his Honda, setting an early 1m42.6s benchmark.
But Lorenzo was able to respond, producing a 1m42.422s for Yamaha to claim the top spot.
Although Pedrosa improved, he had to settle for second, just 0.023 seconds adrift.
Tech 3 Yamaha rider Crutchlow then put himself into a contention with a lap only 0.070s slower than Lorenzo.
Valentino Rossi and Andrea Dovizioso completed the top five.
Alvaro Bautista hung on to sixth despite crashing at Turn 1 late on.
Marc Marquez had a low-key first session and was only ninth, behind Stefan Bradl and Nicky Hayden.
CRT pacesetter Aleix Espargaro jumped into the top 10 with his final lap, demoting Andrea Iannone.
Michele Pirro was back in 13th on the Ducati lab bike, entered in place of the injured Ben Spies at Pramac this weekend.