Treviso (13) 33
A late drop-goal from Ceri Sweeney rescued a win for the Dragons
Tries: De Gregori, Borges, Sgarbi
Cons: Goosen 3
Pens: Goosen 4
Dragons (25) 35
Tries: Charvis, R Thomas, Gomer-Davies, Mustoe
Cons: Sweeney 3
Pens: Sweeney 2
Ceri Sweeney's late drop-goal earned Newport Gwent Dragons a bonus-point Heineken Cup win after a fierce fightback from Benetton Treviso.
Tries from Colin Charvis, Rhys Thomas and Rhodri Gomer-Davies gave Dragons a 25-13 lead at half-time, Nicolas De Gregori replying for Treviso.
Richard Mustoe got the Dragons' crucial fourth try but the Italians hit back.
Lucas Borges and Alberto Sgarbi tries, plus Marius Goosen's boot, put Treviso ahead only for Sweeney to strike.
Sweeney and Goosen twice swapped penalties in the early stages to leave the sides locked at 6-6.
But a loose kick then opened the doors for the Dragons' first try.
Kevin Morgan scooped up possession midway inside Treviso's half and beat two men before Paul Emerick sent captain Charvis over after 18 minutes, Sweeney adding the conversion.
Just two minutes later the Welsh were in for a second, this time through prop Thomas, after Morgan's cross-field kick found Luke Charteris in space and his basketball pass set the front-row on his way.
Sweeney's conversion was wide but the Dragons led 18-6 until the 33rd minute when Gomer-Davies extended it further.
The Dragons pressed left and right before American Emerick was held up inches short of the line and Gomer-Davies followed up, picking up and diving over for a try.
It was not until first-half injury time that the home crowd had something more to cheer when prop De Gregori steamed over to hand Treviso a lifeline.
That hope looked to have evaporated when Mustoe scorched through within two minutes of the restart.
The wing darted on to Sweeney's inside pass and galloped in from 40 yards out to secure a bonus point, Sweeney's conversion putting the visitors 32-13 ahead.
But Treviso launched a stunning comeback at the Stadio Comunale di Monigo and captain Goosen was at the heart of it.
Dragons prop Thomas was shown a yellow card after 45 minutes for his team's persistent infringements and five minutes later Argentina wing Borges raced onto Robert Barbieri's pass to score.
Sweeney missed the chance to steady the ship when his penalty drifted wide and Treviso capitalised when Sgarbi beat Mustoe with ease to score the Italians' third try.
Goosen added the conversion as well as two long-range penalties to put the home side 33-32 ahead 15 minutes from time.
But the Dragons switched back on and Sweeney's late drop-goal was enough to secure five points.
Treviso coach Franco Smith:
"We made a lot of mistakes in the first half especially with the tackles we missed.
"We are developing with every game and if we can sort out those basic mistakes then I believe that first win is just around the corner."
Dragons coach Paul Turner:
"It was almost as if the players thought we had scored too many points and wanted them to make a game of it.
"That doesn't make my job any more pleasurable but we showed character and in the end we got our campaign up and running.
"Treviso came back very well and for a while two or three of our wheels came off. Thankfully the fourth stayed on and we finished with maximum points."
Benneton Treviso: Williams; Borges, Horak, Goosen (capt), Sgarbi; Marcato, Semenzato; De Gregori, Sbaraglini, Costanzo, A. Pavanello, van Zyl, R. Barbieri, Louw, Kingi.
Replacements: M. Barbieri for Costanzo (6), Picone for Semenzato (49), Orlando for R. Barbieri (51), Johnson for A. Pavanello (63), VIdal for Sbaraglini (70), Mauger for Horak (75), R. Barbieri for M. Barbieri (80). Not Used: Palmer.
Dragons: Morgan; M. Thomas, Emerick, Gomer-Davies, Mustoe; Sweeney, A. Williams; Black, S. Jones, R. Thomas, Charteris, A. Jones, Charvis (capt), Parks, Owen.
Replacements: Daly for S.Jones (60), Bearman for A. Jones (60), Gustafson for Black (66), W. Evans for A. Williams (66), Ringer R.Thomas (83).
Not Used: A. Thomas, Smith.
Referee: Rob Debney (England).