In 82 healthy children and in asthmatic children before and during positive allergen provocation test, airway resistance (Raw), airway conductance (Gaw), specific airway resistance (SRaw), and specific airway conductance (SGaw) were measured by body plethysmography during quiet breathing. Raw over total flow range (Raw t) and Raw at a flow rate of 0.5 liter/sec (Raw 0.5) are compared: Raw 0.5 is 10.3% smaller and shows a smaller coefficient of variation in healthy children. This is interpreted as a less important influence of variations of glottis opening. SRaw t mean value is 7.08 hPa . sec; SGaw t mean value is 0.141 hPa-1 . sec-1. In asthmatic children, Raw 0.5 proves to be a more sensitive parameter for the evaluation of inhalation provocation tests than Raw t. The most sensitive indices of obstruction in the central and more peripheral bronchi are SRaw 0.5 and SGaw 0.5.