The European Cup rugby superpowers Munster and Leicester put Italian opponents to the sword on as American winger Takudzwa Ngwenya grabbed a stunning hat-trick to steer Biarritz closer to the quarter-finals.
Double champions Munster, defeated by Northampton in their opening pool one clash, saw off Treviso 41-10 after surviving a major scare when the Italians, who stunned French champions Perpignan last week, took a 10-0 lead.
Australian winger Brendan Williams and England Sevens captain Andy Vilk scored for Treviso to send shockwaves through Thomond Park.
But Munster hit back with tries from Paul Warwick and Ian Dowling to take a 12-10 interval lead.
The Irishmen then stretched their lead after the interval taking their try total to seven with Denis Leamy, Denis Fogarty, David Wallace, Ian Dowling and Jean de Villiers all crossing.
Leicester, also former double European champions, followed up their 32-32 draw with the Ospreys with a bonus-point 46-11 victory over Viadana in Pool Three.
Kiwi star Scott Hamilton grabbed a hat-trick while Johne Murphy, Tom Croft, Lucas Amorosino and a penalty try handed the Tigers victory.
Biarritz secured their second successive win in Pool Two with a 42-15 win over Gloucester.
The French side defeated Glasgow 22-18 in their group opener and now have nine points to lead Newport-Gwent Dragons who saw off the Scots 22-14.
Ngwenya was the star of the show, sprinting 40 metres for his spectacular first try.
Ayoola Erinle and Valentin Courrent also scored for Biarritz with Tom Voyce and Jake Boer scoring Gloucester's two tries.