Respirosonography was used to analyze lung sounds and breathing patterns in 16 infants with acute bronchiolitis who were treated with nebulized salbutamol (albuterol). Wheezing was measured as a proportion of respiratory time (time spent wheezing [Tw]/total time [Ttot]). A decrease of 10% or greater in Tw/Ttot or a reduction in Tw/Ttot to less than 2% was considered a positive response to salbutamol. Seven infants responded to the salbutamol, and nine did not. In responders, Tw/Ttot decreased from 47% +/- 26% to 20% +/- 25% (mean +/- SD), and the respiratory rate decreased from 65 +/- 8 to 57 +/- 7 breaths per minute. In nonresponders, mean Tw/Ttot either did not change or increased, and there was no significant change in respiratory rate (53 +/- 10 breaths per minute before salbutamol inhalation and 56 +/- 9 breaths per minute after salbutamol inhalation). Complex repetitive waveforms, different from the sinusoidal waveforms of typical wheezing, were observed in 14 of 16 infants. Our findings add supportive evidence to the clinical impression that some infants with bronchiolitis respond to salbutamol. Respirosonography provides a noninvasive method for objective clinical assessment of young, wheezy children.