As has been the case on several occasions this season, Pastor Maldonado set the pace in free practice ahead of the GP2 Series finale at Monza, although the terrible weather conditions played their part in the proceedings.
With an earlier thunderstorm flooding the circuit causing a delay to what would become a shortened session, Maldonado was on fine form to keep his Piquet Sports machine pointing in the right direction to edge out, surprisingly, Alberto Valerio by just 0.015secs.
Although the track began to dry slightly towards the end of the session, nearly every driver managed to miss their braking point for the chicanes, serving to tighten up the order. Nonetheless, the only major problems to report were Karun Chandhok spinning off into the gravel at the Parabolica, while Diego Nunes damaged his suspension at Ascari to end his session early.
Behind Maldonado and Valerio, Mike Conway was third quickest in the Trident Racing machine, who in turn was ahead of Lucas di Grassi, the Campos driver looking for a good result this weekend to improve the Spanish team's chances of a surprise team title.
Spa winner Romain Grosjean was fifth quickest, ahead of Davide Valsecchi, the home favourite joining Durango team-mate Valerio in the top six as the team seek to get themselves off the bottom of the standings this weekend.
Arden duo Luca Filippi and Sebastien Buemi were next up, marginally ahead of title contender Bruno Senna, the Brazilian a lacklustre ninth, but still way up on leader Giorgio Pantano, the Italian struggling with the conditions down in 23rd.
Andy Soucek rounded out the top ten in a 25-strong field, depleted by one following the announcement that BCN will run a single car for Carlos Iaconelli this weekend.