The deal, still to be approved by shareholders, will see the private equity affiliate of Goldman Sachs repay USI's current debt obligations. Shareholders will be offered $17.00 per share.
David Eslick, USI chairman and chief executive, said: "After careful analysis, the special committee and board have endorsed this transaction as being in the best interest of our stockholders.
"Our new partner is a world-leading private equity firm that believes in our commitment to investing in our people and is committed to working with us to deliver the most value for our clients and customers."
Henry Cornell, a managing director at GS Capital Partners, said: "Goldman Sachs has a long and successful record of investing in the financial services industry. We know that the success of our investment will be dependent on the talents and commitments of USI's employees. We look forward to investing in the continued growth of USI, in this next chapter."
USI targets the small business market self-insurance, group dental, medical and life insurance products as well as pension plans and other specialist areas.
The deal is expected to be completed in the second quarter of 2007.