Bullhorn Inc., a recruiting software firm headquartered in Boston, announced this morning that it has been acquired by Vista Equity Partners, a private equity firm with $6.6 billion in committed capital. Financial details were not disclosed.

UPDATE 6/14/12 9:02: Techcrunch reports the deal as in “the lower end of hundreds of millions of dollars.”

Founded in 1999, the firm had a banner year in 2011, with 40 percent revenue growth and the addition of 400 new clients. The firm’s last big fundraise was a $26 million Series D in 2008, from General Catalyst and Highland Capital at a $40 million valuation. Bullhorn’s SaaS offerings include essentially a CRM specifically for recruitment and staffing.

“Our great customers and employees have afforded Bullhorn exponential growth over the last decade,” said Art Papas, co-founder and CEO of Bullhorn, in a release. “We’re thrilled to deliver such an outstanding return to our stockholders and to continue to build upon our success with the great team at Vista. Vista’s financial strength and extensive software industry experience make them an ideal partner to help us realize our aggressive plans for product development and global expansion while maintaining high levels of satisfaction and support for our current customers.”

The company estimates that its software has supported $100 billion in client revenue.

“Forty percent growth year-over-year is impressive at any time, but achieving thatlevel of growth in a challenging economic climate is an even greater testament to the strength of the Bullhorn team. Bullhorn has shown that innovation can drive incredible growth in any economy,” said Alan Cline, principal and co-head of Vista Equity Partners Foundation Fund. “By combining our resources and expertise with this great management team and the talented employees of Bullhorn, we see a tremendous opportunity on the horizon as we work together to fuel the next stage of the company’s growth.”

If you haven’t already, check out Papas’ post for us yesterday: 5 Common Myths About Hiring in the Hub.