The experiment reported here attempted to investigate the nature of both intrinsic, unlearned temporal parameters as well as learned, language-specific durational properties in the speech of young children. Developmental aspects of several temporal parameters were investigated in the speech of ten 2 1/2 to 3-year-old and ten 4 to 4 1/2-year-old English-speaking Children; ten adults served as a control group. These parameters were: (a) overall word and segment duration; (b) voice onset time; (c) place of consonantal articulation and duration; (d) consonantal voicing and duration; (e) consonant effects on vowel duration; (f) effects of syllable position on vowel and consonant duration; and (g) effects of stress on vowel and consonant duration. Each subject produced ten repetitions of nine nonsense words. Both groups of children typically revealed word and segment durations which were longer than those of the adults, but speech segment durations of both groups of children reflected intrinsic properties similar in magnitude to those of the adults. Although absolute duration increments due to language specific variables were greater for the children than for the adults, both groups of children behaved very much like the adults with regard to proportional increments of segments. The only extensive departure of the children from adult durational properties was observed in the production of the voiceless stop consonant /t/. Despite various temporal differences between the speech of children and that of adults, it was concluded that children possess timing control systems which are more sophisticated than has previously been suggested. (Author/AM)