Now turning to the financial results we announced earlier. As you've seen in today's news release, Cubist has delivered strong results from the top and bottom line in the second quarter of 2012. In a year focused on execution, we continue to see important progress against key goals for the year.
Our total revenues for Q2 2012 were $231 million, this is our second consecutive quarter with year-over-year top line growth of 30%. Operating income for the quarter is $61.5 million. This is an $86 million positive swing year-over-year, which reflects the impact of $82 million of contingent consideration expense on GAAP operating income in the year ago quarter.
On the top line, there are multiple contributors to our strong results this quarter. CUBICIN momentum in the U.S. continues to be the most important contributor to our top line growth. Q2 net revenues in the U.S. grew 19% versus a year ago, resulting in our first $200 million quarter in the U.S. for CUBICIN.
CUBICIN international revenues from our x U.S. partners in Q2 totaled $11.4 million, up 47% versus Q2 a year ago. I'm pleased with the uptick we have seen in international results through the first half of 2012.ENTEREG results also contributed to our top line in Q2. In our second quarter of commercializing this product, which we brought in with the acquisition of Adolor late last year, we achieved just under $10 million in net revenues. As we begin Q3, we are, as planned, increasing our call universe for ENTEREG to a significantly larger percentage of the hospitals for clinical business managers call-on in the U.S. As Rob will discuss, an important component of this expansion will be some adjustments we are making to incorporate key learnings in the first 6 months of the relaunch. Read the rest of this transcript for free on seekingalpha.com