Reigning Pro14 champions Leinster overcame stern resistance from Benetton Treviso to kick off the new campaign with a 32-27 win.
Dave Kearney's hat-trick helped the Irish province to a bonus-point victory in Italy, despite the visitors having several of their star names away at the Rugby World Cup.
Leinster raced into a 10-0 lead – Ross Byrne kicking a penalty and converting Adam Byrne's try – before Benetton came roaring back.
Derrick Appiah and Tomas Baravalle touched down in quick succession and Ian Keatley proved accurate with the boot to give Benetton the lead.
Kearney then took centre stage, scoring key tries just before the break and five minutes into the second half.
Another rally from the home side, during which Luca Sperandio crossed the whitewash, set up a tense finale but Kearney's converted try and a late penalty ensured a winning start for Leinster.
Munster, losing semi-finalists last season, were 39-9 bonus-point winners over the Dragons, while Cardiff Blues produced a second-half revival to defeat Southern Kings 31-27.
Elsewhere, Scarlets downed Connacht 18-10 and Edinburgh eased past Zebre 50-15