Nico Terol, who has won the last two races since returning from injury, kept the pressure on 125cc title leader Marc Marquez by leading Friday practice for the San Marino Grand Prix.
Marquez, Terol and Pol Espargaro start this weekend's eleventh round covered by just five points at the top of the standings - Marquez having fallen from the lead last Sunday at Indianapolis, then demoted from fifth to tenth by a post-race penalty.
Back on track just five days later, Terol put his Aspar Aprilia back on top of the timesheets by 0.252sec from the Red Bull Ajo Derbi of Marquez, with Espargaro 0.477sec from the top in third for Tuenti Derbi.
Espargaro's team-mate Efren Vasquez was fourth after late technical troubles, with Indy runner-up Sandro Cortese fifth on the second Ajo bike and the last rider within one-second of Terol.
Brits Bradley Smith and Danny Webb were seventh and ninth.
Friday practice - Misano:
1. Terol (Aprilia) 1m 44.229s
2. Marquez (Derbi) +0.252s
3. Espargaro (Derbi) +0.477s
4. Vazquez (Derbi) +0.778s
5. Cortese (Derbi) +0.860s
6. Rabat (Aprilia) +1.201s
7. Smith (Aprilia) +1.209s
8. Koyama (Aprilia) +1.650s
9. Webb (Aprilia) +1.658s
10. Krummenacher (Aprilia) +1.693s