Abstract: The percentage of correct identification of 6 vowels (monophthongs) from the standard colloquial Chinese was studied in various syllable durations. When the syllable duration was kept longer than 60msec, correct identification of vowels remained on a high percentage (above 95%). When the syllabe duration became, from 60 msec on, shorter and shorter, the percentage of correct vowel identification gradually dicreased. As the syllable duration was made shorter than 8-13 msec, vowel identification became impossible. Analysis of the identification errors showed that they happened more often among those vowels, whose articulation and acoustical properties were closer. In the discussion the role of signal duration in vowel identification and in pitch differentiation was compared.