The Beastie Boys's appearance at Lollapalooza 2009 is now confirmed. The line-up for the Chicago music festival, which takes place August 7-9, was officially announced today. Advance tickets are available to purchase HERE [DEAD LINK].

Beastie Boys attended the premiere of Grey Gardens, a HBO film based on the 1975 documentary by the Maysles Brothers, at the Ziegeld Theater in New York City on April 14. The film, which stars Drew Barrymore and Jessica Lange, was executive produced by Adam Horovitz's sister.

See more photos of the Beastie Boys at the Grey Gardens premiere HERE [DEAD LINK].

Beastie Boys will be headlining one day of the three-day Outside Lands Festival, which takes place August 28-30 in San Francisco. The announcement was made in an advertisement posted on the San Francisco Chronicle's web site (see above). The full line-up for the festival will be posted later today on the festival's official web site. Ticket presale begins this Wednesday (April 15).