Winger Michael Roberts scored a hat-trick as defending Heineken Cup champions Wasps secured a bonus-point win at Italian side Calvisano.
Calvisano (3) 22
Tries: Raineri, Fraser, De Carli
Cons: Fraser 2
Wasps (26) 31
Tries: Roberts 3, Lock, Shaw
Cons: Brooks 3
When Wasps romped into a 26-3 half-time lead it looked as though they were going to run away with the game.
But the hosts fought back with Giovanni Raineri, Gerard Fraser and Giampiero De Carli scoring tries.
In addition to Roberts' hat-trick Wasps' other tries came from Mark Lock and returning England lock Simon Shaw.
Calvisano started strongly and opened the scoring with a Gerard Fraser penalty in the sixth minute but Wasps soon took the lead.
Winger Roberts, a former England Under-16 player, scored his first try and he was followed over the line by Lock to give Wasps a 12-3 lead after 20 minutes.
Shaw marked his comeback game with a try after James Haskell's break and Roberts grabbed his second try of the match to give Wasps a four-try bonus point moments before the interval.
Calvisano stopped the rot early in the second half with a try to Italy centre Raineri, converted by Fraser.
But it was Roberts' day and he completed his hat-trick in the 45th minute with a stunning run that started in his own half.
Calvisano hit back in the 53rd minute with a try to the influential Fraser and although they cut the gap to nine points with a De Carli score with 10 minutes to go, Wasps had already done enough to secure the points.
Calvisano: Vaccari, Nitoglia, Raineri, Zanoletti, Vodo, Fraser, Griffen, Bocca, Intoppa, Perugini, Ngauamo, Purll, Mandelli, Elisara, Zaffiri.
Replacements: De Carli, Castrogiovanni, Bernabo, Candiago, Pratichetti, Mulieri, Ravazzolo.
Wasps: Voyce, Lewsey, Waters, Hoadley, Roberts, Brooks, Biljon, Dowd, Greening, Nwume, Shaw, Hart, Lock, Rees, Haskell.
Replacements: Leota, Mackenzie, Skivington, Worsley, Dawson, King, Erinle.