Bottom club Aironi survived a late fightback to shock high-flying Munster in the Pro12 League.
Heineken Cup quarter-finalists Munster were missing key players because of injury and the Six Nations.
And despite a strong finish, the Irish team never recovered from a 15-3 half-time deficit against their lowly opponents in Italy.
First-half tries by Nicola Cattina and Gabriel Pizarro helped Aironi to their fourth win of the season.
Munster managed only a Scott Deasy penalty in reply as Aironi made the most of their attacking opportunities at the Stadio Luigi Zaffanella.
Munster eventually stirred in the final quarter, collecting a penalty try and touchdown from centre Lifeimi Mafi, but were unable to make the pressure count and overturn Aironi's lead.
Munster coach Tony McGahan was forced to make eight changes to the side which beat Newport Gwent Dragons the previous weekend.
Aironi: T Tebaldi; R Pavan, M Pratichetti, G Pizarro, S Sinoti; L Orquera, T Keats; J Sole, N Cattina, F Ferrarini; C Del Fava, G Biagi; L Romano, R Santamaria, M Aguero.
Replacements: F Ongaro, A De Marchi, S Perugini, F Cazzola, E Caffini, G Bronzini, N Olivier, A Benettin.
Munster: F Jones; D Hurley, S Tokula, L Mafi, S Zebo; S Deasy, D Williams; W du Preez, M Sherry, S Archer; B Holland, M O'Driscoll capt; Dave O'Callaghan, T O'Donnell, P Butler.
Replacements: D Fogarty, M Horan, BJ Botha, I Nagle, D Wallace, C Sheridan, I Keatley, L O'Dea.