Keeping with avant-garde form the film is a series of apparently unrelated, at times offensive scenes that attempt to shock the film's viewers. On the other hand, the film breaks from avant-garde tradition by focusing on content as well as on cinematic form: surprising camera angles, film "tricks", etc.
The film opens with a scene in which a woman's eye is slit by a razor, and continues with a series of surreal scenes - a man pokes at a severed hand in the street with his cane, a man drags two grand pianos containing dead and rotting donkeys the tablets of the Ten Commandments and live priests, a man's hand has a hole in the palm from which ants emerge, a woman's pubic hair attaching itself to a man's face.
Critics have suggested that Un Chien Andalou can be understood as a typically Buñuelian anti-bourgeois, anticlerical piece. For instance, the man dragging a piano, donkey and priests being deciphered to mean that the man's progress towards his goal is hindered by the baggage of conventional society which he is forced to bear.
Another interesting thought is that the slicing of the eye in the opening scene can be understood as Buñuel "attacking" the films viewers (Buñuel himself plays the man wielding the razor).
The film is heavily referenced in the Pixies's song "Debaser".