Dragons: (3) 22
The Dragons made hard work of beating Calvisano
Tries: A. Thomas, Charteris
Con: Sweeney (2)
Calvisano: (8) 15
Tries: Spragg, Bernabo
Pens: De Marigny
Newport Gwent Dragons booked their place in next season's Heineken Cup after surviving a major scare against Italians Calvisano at Rodney Parade.
The visitors opened up a 15-3 play-off lead after 46 minutes with tries from Warren Spragg and Valerio Bernabo.
Aled Thomas and Luke Charteris crossed to level the scores on 70 minutes.
Roland de Marigny missed a penalty to put Calvisano ahead and then home centre Paul Emerick finished off a fine move on 78 minutes to clinch victory.
Emerick was the villain last season when he scored the winning try in Overmach Parma's Heineken Cup play-off win against the Dragons.
The American had warned his team-mates to expect a "brawl of a game" against Calvisano, and his worst fears were realised as the visitors completely dominated the first half.
De Marigny opened the scoring with a third-minute penalty, before the Dragons suffered a blow as captain full-back Kevin Morgan left the field 10 minutes later with a knee injury.
Sweeney's penalty got the Dragons on the board, but only after De Marigny had missed two golden opportunities to reach the lead from kickable penalties.
With half-time approaching, Calvisano scored the try their dominance deserved when winger Spragg crossed after a break by replacement Michael Gallinetti.
The frowns deepened around Rodney Parade six minutes into the second half when Bernabo brushed aside Alex Walker's weak tackle to score, with Gallinetti converting.
The Dragons finally realised they needed to raise their game, and Gareth Wyatt deleivered the spark to launch the comeback.
After the winger had collected his own kick ahead inside Calvisano's 22, the forwards took the ball on and then Sweeney's superb cut-out pass found unmarked replacement Thomas on the left-wing.
Second-row Charteris then levelled the scores when he stretched his 6ft 10in frame over in virtually the same spot after a period of heavy Dragons pressure.
Sweeney missed the conversion, but he was left off the hook when Emerick touched down with extra-time looming.
Dragons: Morgan (capt); Wyatt, Emerick, Maule, M. Thomas; Sweeney, Walker; Black, Jones, Harrison, Gough, Charteris, Bearman, Owen, Ringer.
Replacements: A. Thomas for Morgan (12), P. Dolman for Maule (55), Baber for Walker (47), Daly for Jones (54), Hall for Gough (50).
Not Used: Corsi, Lydiatt.
Calvisano: Buso; Nitoglia, Pratichetti, Downey, Spragg; De Marigny, Griffen (capt); Bocca, Ghiraldini, Cittadini, Ngauamo, Bernabo, Zanni, Purll, Persico.
Replacements: Gallinetti for Buso (31), Zanoletti for Downey (72), Patelli for Griffen (63), Vigne-Donati for Bocca (60).
Not Used: Intoppa, Moore, Cattina.
Ref: Rob Debney (Leicestershire).
Referee: Rob Debney.