Aprilia's Marco Melandri picked up where he left off in Sepang by leading first practice on the Italian circuit, but was bettered by compatriot Giugliano in a red flag-affected second session.
The session was initially stopped when the MV Augusta of Michael Savary caught fire, and there was a further delay soon after when Aaron Yates' Team Hero EBR stopped on track with an apparent engine problem.
However, when the riders returned to complete their time on the track, Giugliano showed no ill effects of being made to wait around.
The Italian Ducati rider crossed the line in one minute and 36.370 seconds to edge Kawasaki's Tom Sykes (+0.127secs) - the current world championship leader - into second.
Sykes completed his best lap just three hundredths of a second quicker than Melandri (+0.130secs), who will take great confidence from his beginning to the weekend following his double victory in Malaysia last time out.
Chaz Davies (+0.266secs) finished fourth in another positive showing from Ducati, while Loris Baz (+0.291secs) and Alex Lowes (+0.328secs) rounded off the top six.