In my consumer guide mode, I should first mention one very simple way to tell whether you might like Bob & Carol & Ted & Alice--do you like films that are almost all dialogue? If not, you should stay away from this one, because that's 90 percent of it. It's very poignant and often clever dialogue, but dialogue nonetheless.
A dialogue-laden film can't succeed without grand performances, and we get just that from the four principal actors. I was especially impressed with Elliott Gould, partially because I haven't always liked him in other films.
Bob & Carol & Ted & Alice deals with normal, middle class couples in the late 1960s who are trying to deal with and adapt to cultural spillover from the then-popular hippie movement. Bob (Robert Culp) is a filmmaker who wants to do a documentary on something of a "personal exploration retreat". While initially checking the retreat out, he and wife Carol (Natalie Wood) completely forget about the film and become wrapped up in the personal exploration taking place. When they get back home, they introduce their new approach to life and interpersonal communications to best friends Ted (Gould) and Alice (Dyan Cannon), who think that Bob and Carol have gone a bit looney. They really think that when later Carol suddenly announces that Bob had a brief affair with another woman and they're both happy with it. Bob & Carol & Ted & Alice then becomes primarily an exploration of how average middle class folks deal with attempts to incorporate hippie sexual liberation beliefs into their lives.
It's a great idea, handled with aplomb by writer-director Paul Mazursky and co-writer Larry Tucker. Interestingly, Mazursky revisited the same basic ideas in Scenes from a Mall (1991), which enabled him to show how much popular cultural attitudes had changed between the late 1960s and the early 1990s. Here, the cultural clash between hippies and the middle class allows him to adeptly explore a number of themes, ranging from hippie ideals as a trend to be followed rather than ideals that are believed in for their own sake, to the psychological conflicts of intrinsic desires either against other intrinsic desires or against cultural conditioning and expectations. Mazursky employs an artful restraint so that these themes are only implicit, but they're definitely present.
The ending of the film is highly unusual but effective, although especially for me--as someone who champions extremely liberal sexuality and thinks monogamy isn't really a great idea--there was a contradictory one-two punch of being disheartening, then shortly after uplifting. The effect of the final scene was a bit enigmatically ambiguous. But I don't think that's a bad thing at all.