The riders had to contend with intense heat on Sunday
Leonardo Bertagnolli's breakaway effort was rewarded as the Italian took the Giro d'Italia's 15th stage.
Bertagnolli of the Diquigiovanni team finished 54 seconds ahead of Belgium's Serge Pauwels in the 161km stage from Forli to Faenza.
Marco Pinotti of Italy took third, while Russian Denis Menchov of Rabobank maintained his overall lead.
Menchov's lead is just 34 seconds and Monday's stage - 237km long, with a steep finish - could be decisive.
Stage 16 begins in Pergola and ends in Monte Petrano.
The 2007 Giro winner Danilo Di Luca of Italy is second overall, with American Levi Leipheimer of the Astana team in third, 45 seconds behind Menchev, while pre-race favourite Ivan Basso, the 2006 champion, is just over three minutes behind the leader.
Seven-times Tour de France winner Lance Armstrong, competing in his first Giro after recovering from a broken collarbone, was nearly three minutes behind Bertagnolli and lies 13th overall, almost 8-1/2 minutes adrift of Menchov.
Meanwhile Spain's Alejandro Valverde, who is banned from racing in Italy, won the Tour of Catalunya.
Valverde finished 15 seconds ahead of Ireland's Daniel Martin, with Spain's Haimar Zubeldia, 22 seconds back.
The world's top-ranked rider in 2008, Valverde was banned by Italy's Olympic Committee (CONI) for two years on 11 May.
CONI said blood samples Valverde gave at a doping control when last year's Tour de France entered Italy for a stage matched DNA from code-named bags of blood discovered in Spain's Operacion Puerto investigation, launched in 2006.
Valverde, who is expected to launch an appeal before the Court of Arbitration for Sport, has repeatedly protested his innocence and continues to race outside Italy.
Stage 15 results (Sunday):
1. Leonardo Bertagnolli (Italy / Diquigiovanni ) 4hrs 18mins 34secs
2. Serge Pauwels (Belgium / Cervelo ) +54s
3. Marco Pinotti (Italy / Columbia ) +54s
4. Lars Bak (Denmark / Saxo Bank ) +54s
5. Marco Marzano (Italy / Lampre ) +56"
6. Andriy Grivko (Ukraine / Team ISD ) +1:27"
7. Mauro Facci (Italy / Quick-Step ) 1:49"
8. Tadej Valjavec (Slovenia / AG2R ) +1:51"
9. Eduard Vorganov (Russia / Xacobeo ) +1:51"
10. Kevin Seeldraeyers (Belgium / Quick-Step ) +1:56"
1. Denis Menchov (Russia / Rabobank ) 62hrs 54mins 23secs
2. Danilo Di Luca (Italy / Team LPR ) +34"
3. Levi Leipheimer (U.S. / Astana ) +45"
4. Franco Pellizotti (Italy / Liquigas ) +2:00"
5. Carlos Sastre (Spain / Cervelo ) +2:52"
6. Ivan Basso (Italy / Liquigas ) +3:03"
7. Michael Rogers (Australia / Columbia ) +3:05"
8. Marzio Bruseghin (Italy / Lampre ) +5:26"
9. David Arroyo (Spain / Caisse d'Epargne ) +6:01"
10. Thomas Lovkvist (Sweden / Columbia ) +6:26"
13. Lance Armstrong (U.S. / Astana ) +8:28"