This study examined vowel duration in a language (Malayalam of Southern India) whose vowels contrast phonemically in length. A number of acoustic parameters (formant frequency, fundamental frequency, and intensity) concomitant with duration during stimulus production were examined for their potentially contributing effects. Ten CVCV words, differing only with respect to whether the first vowel was short or long, were uttered in a standard frame and later identified by speakers of Malayalam. The average durations of long vowels were approximately twice that of their short vowel counterparts. Analysis of the other acoustic parameters revealed only small and inconsistent differences between the short and long vowel pairs. It was concluded that the linguistic distinction between short and long vowels may reside in the single parameter of duration.