The survival time of Bordetella bronchiseptica (phase I and III) has been determined at a temperature of 21 degrees C and 27 degrees C and at a relative humidity of 32%, 58% and 76% in a rotating aerosol chamber. The highest survival time (118.8 min half-life time) has been found at 21 degrees C and 76% relative humidity in B. bronchiseptica (phase I). An increasing temperature (from 21 degrees C to 27 degrees C) causes a lower survival time. The phase I strains react more sensitive to this changing of environment than phase III strains. An increase of relative humidity leads to a higher survival time concerning phase I strains. In contrast phase III strains of B. bronchiseptica react with an increasing survival time. On the basis of the detected half-life time one must suppose an aerogenous distribution of the germ in all stages of animals, especially in intensive husbandry.