The breathing pattern in children with asthma was studied, using respiratory inductive plethysmography. The subjects were 31 children with mild to moderate asthma (15 males, 16 females; aged 6-15 years, average 11 years). The respiratory rate was 25.5 +/- 10.7/min. (mean +/- S.D.) during asthma attacks and 18.4 +/- 5.0/min. between attacks with a significant increase during attacks (P less than 0.001). The expiratory time was 1.774 +/- 0.833 second during attacks, and 2.125 +/- 0.602 seconds between attacks. The expiratory time to total respiratory time ratio (TE/TTOT) was 0.631 +/- 0.056 during attacks and 0.608 +/- 0.035 between attacks. Thus there was a slight prolongation at the time of attack, but the difference was not significant. The tidal volume was increased slightly during mild and moderate attacks. VT/TI (mean inspiratory flow) was increased during attacks. The respiratory pattern was thoracic during attacks and changed to the abdominal pattern with improvement.