This study explored the relation between phonological short-term memory and auditory–sensory processing in 7–9-year-old children. Twenty-four participants performed a pseudoword repetition test. The mismatch-negativity (MMN) component of auditory event-related brain potentials was obtained from 9 participants with the highest and 9 participants with the lowest scores on the test. The MMN indexes short-term auditory–sensory memory, including auditory–sensory representations for speech. It was recorded to just perceptible /baga/–/baka/ bisyllabic and easily discriminable 1000/1100-Hz tone contrasts with interstimulus intervals of 350 and 2,000 ms. The high and low repeaters differed significantly in MMN amplitude to speech stimuli at the shorter interstimulus interval. Thus, the accuracy of auditory–sensory processing seems to affect phonological short-term representations in school-age children and therefore may play a role in vocabulary development.