Ulster made it two wins out of two in the Pro12 with a battling victory in a scrappy game against Aironi.
On a sweltering day in Viadana, Ulster led 12-3 after tries by Ian Whitten and Dan Tuohy.
Aironi hit back to lead after forward Nick Williams got over for a try but a long-range Ian Humphreys penalty gave Ulster a 15-13 half-time lead.
A third Naas Olivier penalty edged Aironi ahead again but Craig Gilroy's 59th-minute try was enough for Ulster.
The Irish province led 25-16 thanks to the conversion from Humphreys and they held on after another Olivier penalty had given Aironi hope.
Ulster did have a late chance to grab a bonus point but, for the second week in a row, had to settle for the three tries.
They seemed to be destined for a routine win on the evidence of the opening half hour.
After early penalty misses by Aironi's former Cheetahs fly-half Naas Olivier and Ulster number 10 Ian Humphreys, the visitors got the opening score through Ian Whitten's 18th-minute try.
Pedrie Wannenburg made good ground before Willie Faloon supplied the final pass for Whitten, playing on the wing for a second match, to finish well by beating a defender in the corner.
Humphreys failed with the conversion and Olivier got Aironi off the mark with a penalty.
Ulster looked as if they might be heading for an expected victory when they got a second try in the 26th minute.
Humphreys was involved in the move twice, firstly kicking ahead for Gilroy, and then supplying the pass for Tuohy to touch down.
Fly-half Humphreys added the extras this time and Ulster looked in command with a 12-3 advantage.
Aironi, though, hit back with the try from Williams, converted by Olivier who also added a second penalty to have the home side ahead at 13-12.
Former Munster number eight Williams forced his way over, under the Ulster posts, after Nevin Spence had done well to hold up the initial charge.
Humphreys then landed a superb penalty from five metres inside his own half to give Ulster a 15-13 lead at half-time.
Aironi regained the lead after an Ulster front row offence at the scrum led to Olivier kicking his third penalty.
Ulster seemed to be lacking in confidence but a fine run by scrum-half Paul Marshall saw them set up a third try.
Marshall gained about 60 metres and, after a couple of phases, Spence's pass saw Gilroy get over for the try.
The flags did not go up for the Humphreys conversion but referee Neil Hennessey ruled that it had gone over and Ulster led 22-16.
Humphreys kicked another penalty from distance and Olivier landed his fourth for the hosts.
Aironi: Trevisan, R Pavan, Quartaroli, Pizarro, Venditti, Olivier, Tebaldi, Aguero, Santamaria, Staibano, Furno, Biagi, Sole, Cattina, Williams.
Replacements: Giazzon, A De Marchi, Redolfini, Favaro, Viljoen, Bronzini, Benettinuts, G Pavan.
Ulster: D'Arcy, Gilroy, Cave, Spence, Whitten, Humphreys, P Marshall, McAllister, Kyriacou, Cronin, Barker, Tuohy, Wannenburg, Faloon, Henry.
Replacements: Brady, Fitzpatrick, Macklin, Stevenson, Diack, Porter, Jackson, L Marshall.
Referee: Neil Hennessey (Wales)