When an [s] or an [s] fricative noise is combined with vocalic formant transitions appropriate to a different fricative, the resulting consonantal percept is usually that of the noise. To see if the mismatch affects processing time, five experiments were run. Three experiments examined reaction time for identification of [s] and [s], as well as the whole syllable (in one experiment) or only the vowel (in the others). The stimuli contained either appropriate or inappropriate formant transitions, and the vowel information in the noise was either appropriate or not. Subjects were significantly slower in all tasks in identifying stimuli with inappropriate transitions or inappropriate vowel information. Similar results were obtained with stop-vowel syllables in which the release bursts of syllable initials [p] and [k]were transposed in syllables containing the vowels [a] and [u], In the fifth experiment, enough silence was introduced between the initial fricatives and vocalic segment for the vocalic formant transitions to be perceived as a stop (e.g., [stu] from [su]). Mismatched transitions still had an effect on reaction time, as did mismatches of vowel quality. The results indicate that listeners take into account all available cues, even when the phonetic judgment seems to be based on only some of the cues.