Aspar Aprilia's 250cc World Championship leader Alvaro Bautista finished Friday free practice at Mugello on top of the timesheets by 0.244sec from Scot Honda's Hiroshi Aoyama.
Both Bautista and Aoyama, who will start round five just one point apart, set their best time on their 26th and final lap of the hour long session, which took place in bright sunshine.
Hector Barbera put his Pepe World Aprilia into P1 during the session, before being bumped down to third while countryman Alex Debon was fourth. The top Italian was Aoyama's team-mate Raffaele de Rosa in fifth.
Reigning 250cc world champion Marco Simoncelli, who took his first win of the season last time out at Le Mans, was only eighth in front of his home fans and a worrying 1.031sec from Bautista.
23-year-old Balazs Nemeth, singed to replace fellow Hungarian Gabor Talmacsi at the Balatonring Team for the remainder of the season, was 24th and last, some ten seconds off Bautista's pace.
Friday practice - Mugello:
1. Bautista (Aprilia) 1min 53.814sec
2. Aoyama (Honda) +0.244sec
3. Barbera (Aprilia) +0.458sec
4. Debon (Aprilia) +0.560sec
5. de Rosa (Honda) +0.770sec
6. Abraham (Aprilia) +0.847sec
7. Wilairot (Honda) +0.898sec
8. Simoncelli (Gilera) +1.031sec
9. Pasini (Aprilia) +1.306sec
10. Faubel (Honda) +1.628sec