Since speech involves fleeting acoustic events some portions of heard utterances must be parsed and stored on-line in order to be interpreted. Our previous work has shown that in recalling novel series, rhythmic grouping of up to 4 syllables facilitates memory, and this corresponds to size limits on rhythm groups observed in speech. Such results suggest that prosodic groups can correspond to the natural parsing frameworks of memory processing. The present study further investigates this correspondence by means of an event-related potential technique. It has been established that the quality of memory traces of words is associated with variations in the amplitude of the N400 component. We show that variations in the amplitude of the N400 confirm for one subject that words presented in rhythm groups that do not exceed a 4-syllable limit present a better quality of memory trace than words presented in groups of 5 syllables, which rarely occur in speech and do not facilitate recall. Though the present observations are preliminary, our results converge on the point that prosodic grouping can be linked to mnemonic processes and that restrictions on memory may underlie size limits on prosodic groups.