Recent research on 5- to 11-year-old children's perception of stop consonants and vowels indicates that they can generally identify these sounds with relatively high accuracy from short duration stimulus onsets [Ohde et al., J. Acoust. Soc. Am. 97, 3800-3812 (1995); Ohde et al., J. Acoust. Soc. Am. 100, 3813-3824 (1996)]. The purpose of the current experiments was to determine if younger children, aged 3-4 years, can also recover consonant and vowel features from stimulus onsets. Ten adults, ten 3-year olds, and ten 4-year-olds listened to synthesized syllables composed of combinations of [b d g] and [i u a]. The synthesis parameters included manipulations of the following stimulus variables: formant transition (moving or straight), noise burst (present or absent), and voicing duration (10, 30, or 46 ms). Developmental effects were found for the perception of both stop consonants and vowels. In general, adults identified these sounds at a significantly higher level than children, and perception by 4-year-olds was significantly better than 3-year-olds. A developmental effect of dynamic formant motion was obtained, but it was limited to only the [g] stop consonant. Stimulus duration affected the children's perception of vowels indicating that they may utilize additional auditory information to a much greater extent than adults. The results support the importance of information in stimulus onsets for syllable identification, and developmental changes in sensitivity to these cues for consonant and vowel perception.