The focus of this study is the nature of the secondary effects of place of articulation and vowel quality on VOT (and other acoustic properties) in the production of stops in French and English and the consequences of these factors on the perception of VOT continua by speakers of those languages. Although the largest source of differences in VOT is that associated with the voicing contrast, a number of previous studies indicate that both French and English stops show an effect of place of articulation, with velars showing longer VOT than labials or coronals in accord with the general tendencies noted by Lisker and Abramson (1967; see also Volaitis and Miller 1992). However, some modulation of VOT by vowel context has also been reported. Thus, Fischer-Jørgensen (1972) finds that, in French voiceless stops, VOT is longer before a high vowel than before a low vowel. She further reports an interaction between the place of articulation of the consonant and the identity of the vowel. Specifically, for /p/, the longest voicing lags occur before high rounded vowels (/u/ and /y/); but for /t/ and /k/, they are longest before /i/. Yeni-Komshian, Caramazza and Preston (1977: 43) also report longer voicing lags before /i/ than before /a/ or /o/ for unilingual French speakers.