Sex differences in phonological processing were investigated in four experiments. Two experiments required college students to decide whether two five-letter strings matched. Same-case (AA)pairs of letter strings could be matched using physical features, whereas mixed-case (Aa) pairs of letter strings required the mediation of a speech-based code (letter name) for the comparison. Women were significantly faster than men when the comparisons required the speech-based codes. In another experiment, college students read lists of words and lists of pseudohomophones to determine whether there was a sex difference in the computation of phonology for unfamiliar words (assembled phonology). In a final experiment, students read lists of words with phonologically inconsistent spelling patterns to determine whether there was a sex difference in accessing pronunciations of familiar words (addressed phonology). Women were more proficient than men under both of these conditions. Results were interpreted in terms of a female advantage in both prelexical and lexical processing, an advantage that may stem from a sex difference in the quality of the phonological representations.Phonological processing refers to the use of abstract phonological representations for processing oral and written language. According to Chomsky & Halle (1968), phonological transformations of a language connect the phonetic surface structures to underlying lexical and abstract phonological representations. These abstract representations are not "speech sounds" nor are they vocalized or subvocalized speech, though they mediate such activities (Frost, 1998), and they share much in common with the speech-based information that is stored and rehearsed in Baddeley's (1992) phonological loop. These speech-based representations of speech as well as the related articulatory representations are both implicated in cognitive differences between men and women (MeGuinness, 1981).Recent evidence of a sex difference in hemispheric specialization may shed some light on the nature of the sex difference in the use of speech-based codes (Pugh et al., 1997;Shaywitz et al., 1995). During phonological processing, judging whether pronounceable non words rhymed, women on the average showed greater righthemisphere activation (inferior frontal gyrus and extrastriate region) than did men. According to Pugh et al., these regions are believed to be associated with the processing ofletters in a serial and small-grained manner (phonemes and phoneme clusters). Both men and women showed