Bath forwards Will Spencer and Ross Batty both crossed the white line in the first half as Sam Vesty proved his worth, kicking 15 points and securing himself a 45th minute try.
The 2008 tournament champions never looked like losing as they raced away in the second half to secure a bonus point and place them at the top of the table. Travelling to Agen in Round 2 will prove a different challenge, but for now Bath can move forward with a certain degree of confidence.
Having not reached the knock-out stages of the competition since 2005, Agen paved the way for all that to change with a narrow five-point victory over Calvisano at the Peroni Stadium. The two teams exchanged early tries before Agen turned up the pressure with a further three first-half tries against Calvisano's two.
The Agen dominance of the first half was nearly undone as the Italian hosts staged a remarkable late comeback to close the gap to a mere five points at the final whistle, securing an invaluable two bonus points along the way.