In 6/8 time. It is in sonata form, typical of the opening movement of a piano sonata.

Although the composer himself described this movement as "atonal," the actual first theme appears to be centered around B♭. However, skillful chromaticism, the use of tritones, and polyphony obscure this, and the music progresses with an unstable sound where tonality is imperceptible, as indicated by the marking "inquieto" (anxiously/uneasily). Beyond the tonality of this theme, its rhythm is particularly noteworthy. A series of regular, powerful rhythmic patterns, reminiscent of a march despite being in 6/8 time, makes the "atonal" material surprisingly familiar and appealing to the ear. The second theme, played with a change in time signature and tempo (9/8 time, Andantino), also exhibits unstable tonality, yet each of its sections is constructed according to a scale, clearly demonstrating a structural change from the first theme.

As the second theme gradually accelerates, the movement enters the development section. Following the typical sonata form, it is constructed from the themes introduced thus far, while traversing the keyboard freely and reaching a climactic peak of rare intensity for Prokofiev's compositions.

In the recapitulation, only the second theme is briefly restated, concluding abruptly as if cut off, after a coda based on the first theme.