This study examined whether the behavior of the respiratory system during speech production differed between adults and children as a function of articulatory and intensity factors. Changes in the mean cross-sectional area of the rib cage and abdomen were measured and percent vital capacity calculated using respiratory inductive plethysmography. Statistical analysis revealed a number of significant differences between the results for children and adults: (a) At the loud intensity level, the adults used a larger percent of their vital capacity than did the children; (b) Adults went further into their functional residual capacity (FRC) at the loud intensity level than at the comfortable level, whereas the children did not; and (c) At the loud intensity level, children used a greater percent of their vital capacity (VC) while reading a passage containing consonants requiring high lung volume increments than while reading a passage requiring low lung volume increments; the adults did not show this effect. These findings suggest that respiration in children is influenced primarily by articulatory demands and secondarily by intensity demands. Whereas, adult respiration responds primarily to the maintenance of vocal intensity level. Finally, the so-called "lung volume range for speech" used by the children was placed significantly lower in their overall VC range than was that of the adults. This result is coupled with the observation that children consistently encroached further into their FRC than did the adults across all conditions, although the effect reached significance only at the loud intensity level while the children read the high-volume passage.