Five experiments investigated listeners' capacities for perceiving polytonality, in which materials from more than one key are employed simultaneously. The stimulus materials were based on a particularly striking example of polytonal writing from Stravinsky's Petroushka; it outlines in arpeggiated form the tonic triads of two maximally distant major keys, C and F# major. The first experiment demonstrates, using the probe-tone technique, that the two component voices presented in isolation establish the expected keys and that when they are combined some influence of both keys is felt. The second and third experiments indicate, however, that when presented dichotically the two components cannot be separated perceptually; this is attributed to the two voices having the same rhythmic and contour patterns and being sounded in the same pitch range. The fourth experiment replicated the findings of the first three, using listeners very familiar with the particular passage. The final experiment tested an alternative theoretical account, the octatonic collection. Probe-tone ratings following an octatonic scale did not account satisfactorily for the data for the musical passage, but the hierarchy of priorities proposed by Van den Toorn (1983) fit the data better than the major key profiles, especially for the experienced listeners.