The early part of the evening is devoted to charades and lighthearted entertainment. Following a series of toasts offered by the guests, Joe distributes the ecstasy Skye brought them as a gift. As it begins to take effect, the night deteriorates, accusations are made, secrets are revealed, and relationships slowly unravel. Complicating emotions triggered by the drug are the disappearance of Otis and a phone call from Joe's father bringing tragic news about his beloved sister Lucy.
The order in which the toasts were made was determined before the scene was filmed but, with the exception of that offered by Skye, they were ad libbed rather than scripted.
The film's soundtrack includes "I Know a Place" by Petula Clark, "I May Never Go Home Anymore" by Marlene Dietrich, "Comin' Home Baby" by Mel Tormé, "There Is No Greater Love" and "A Lot of Livin' to Do" by Sammy Davis Jr., "Stealing My Love from Me" by Lulu, and the Adagio from the Sonata No. 1 in G minor by Johann Sebastian Bach.
The film premiered at the Cannes Film Festival in May 2001 prior to its limited release in the US the following month. It grossed $4,013,506 in the US and $884,559 in foreign markets for a total worldwide box office of $4,898,065 .
Roger Ebert of the Chicago Sun-Times observed, "The appeal of the film is largely voyeuristic. We learn nothing we don't already more or less know, but the material is covered with such authenticity and unforced natural conviction that it plays like a privileged glimpse into the sad lives of the rich and famous. We're like the neighbors who are invited. Leigh and Cumming . . . are confident professionals who don't indulge their material or themselves. This isn't a confessional home movie, but a cool and intelligent look at a lifestyle where smart people are required to lead their lives according to dumb rules."
In the San Francisco Chronicle, Mick LaSalle said, "Leigh and Cumming save the best roles for themselves, and both their roles reach major emotional crescendoes. Yet to their credit, with all the video in the world at their disposal and nobody to rein them in, they don't indulge themselves. They're both brilliant, spot-on and wonderfully true. The Anniversary Party is probably one of those miracles that can happen only once. Still one can't help hoping that Leigh and Cumming collaborate on another film."
Peter Travers of Rolling Stone stated, "The final result should be a self-indulgent mess - and, in truth, the final third of the film comes close. But until Leigh and Cumming let their actorly urge for high drama blunt their flair for bracing wit and subtle feeling, they turn what could have been an acting stunt into an intimate and compelling study of bruised emotions . . . [They] were fortunate to secure the services of master cinematographer John Bailey, who brings textured marvels of light and shadow to digital camerawork that is often crude in lesser hands. It's only when the guests head for the pool to play truth games on Ecstasy while Leigh and Cumming head for the hills for a Who's Afraid of Virginia Woolf? sparring match that the movie collapses under the weight of its artsy-fartsy ambitions. My advice on how to get the most from this Party is: Leave early."
In Variety, Todd McCarthy said the film "is well observed in many particulars but is too familiar in its basic trajectory to be fresh or compelling . . . All the roles are in good hands, and it's mildly amusing in a voyeuristic way to watch the likes of Paltrow behave as we might imagine stars do at a party . . . Although the digital video imprint is still evident, ace vet lenser John Bailey has gone a long way toward making this look like a celluloid-shot picture, most successfully in the bright, daytime scenes, less so at night or under low lighting conditions, where the images sometimes appear washed out."