The deal is expected to close in the second quarter. Combined, the two vendors will have more than 20,000 customers, and will constitute "the largest company dedicated to the legal information management industry," according to a statement.
Autonomy sees a growing market for e-discovery due to increased litigation and recent regulatory changes, which have "heightened the need to capture and understand information," such as employee communications, the companies said.
Forrester Research has said e-discovery spending will grow to more than $4.8 billion by 2011, up from $1.4 billion in 2006.
Meanwhile, Interwoven's software is in use at 1,200 top law firms and supports 100,000 Web sites, extranets and intranets, according to a statement.
One industry observer and Autonomy shareholder praised the pending acquisition.
"Web content management and search are obvious bedfellows," said Richard Holway, a tech analyst based in the U.K., in a blog Thursday. "Secondly, Interwoven's strongest sector is legal -- again a great fit with Autonomy which has made its reputation in compliance and disclosure."
Analyst firm The 451 Group said in a blog that the deal would leave stand-alone content management vendors such as Vignette "in an even worse position."
Autonomy has made a number of acquisitions in recent years, such as its 2007 purchase of archiving and e-discovery vendor Zantaz for $375 million. The spree has Autonomy "looking more and more like a mini-Oracle every day," the unsigned 451 Group post said.