Ventilatory monitoring devices that require mouthpiece breathing produce a rise in tidal volume (VT), a fall in frequency (f) and alterations in periodicity and variability of breathing components. Together with the introduction of the respiratory inductive plethysmograph, a reliable noninvasive monitoring device of ventilation, major advances have taken place in understanding the significance of the components of the breathing pattern. We measured the breathing pattern of normal subjects utilizing respiratory inductive plethysmography and continuously processed these data with a microprocessor system. The mean values of the breathing pattern components in normal subjects were not affected by age, but the rhythmicity was more irregular in the elderly. The values of breathing pattern components obtained noninvasively by respiratory inductive plethysmography in normal subjects are fairly predictable in limits similar to other tests of pulmonary function.