Advent International has acquired a 38 percent stake in Amscan Holdings Inc., an Elmsford, N.Y.-based maker and retailer of party goods and accessories. The shares were sold in a secondary transaction by existing Amscan backers Berkshire Partners, Weston Presidio and company management. No financial terms were disclosed, except that Amscan generated 2007 gross pro forma revenue of $1.7 billion.

AEA Investors has agreed to acquire convict monitoring company Behavioral Interventions Inc. from Quad-C Management, according to an FTC disclosure form discovered by Dow Jones. No financial terms were disclosed, except that it included some leverage and company management participation. Quad-C had bought Behavioral Interventions from Kohlberg & Co. in 2006.

Bain Capital Partners has completed its acquisition of Contec Holdings Ltd. from American Capital for around $525 million. Contec provides consumer-premise equipment repair services for broadband companies.

BlackEagle Partners has acquired InStar Services Group LP from The ServiceMaster Co., which is owned by Clayton, Dubilier, & Rice. Financial terms weren’t disclosed. InStar is a Fort Worth, Texas-based provider of disaster response, insurance restoration and reconstruction services on the East Coast, Southeast and Texas. Morgan Keegan & Co. served as sell-side advisor.

GenNx360 Capital Partners has agreed to acquire Precision AeroPower Group from GSC Group. PAG provides manufacturing and engineering services to the commercial aerospace, defense, and power generation industries. Financial terms weren’t disclosed.

JPB Capital Partners has acquired Wythe-Will Distributing LLC from Hunt Private Equity Group, for an undisclosed amount. Bank of America Business Capital provided leveraged financing for the deal, which also included equity participation by company management. Wythe-Will is a Williamsburg, Va.-based specialty food distributor to premium grocers and other retailers.

LDC has acquired UK vehicle management group Leasedrive Velo in an £80 million secondary buyout from Lyceum Capital.

Linsalata Capital Partners has acquired Hospitality Mints Inc. from American Capital Ltd. Financial terms weren’t disclosed. Hospitality Mints is a Boone, N.C.-based maker of customized, individually-wrapped promotional mints and candies.

Perseus has agreed to sell its stake in Workflow Management Inc. to blank check acquisition company Enterprise Acquisition Corp. (AMEX: EST), as part of a $669 million merger agreement. Perseus will retain an ownership position. Workflow Management provides print and promotional products and fulfillment services in North America.