In this study, the ability to predict allergenic bronchial reactivity from non-specific bronchial reactivity, measured by free corridor-running, and the level of skin reactivity to whole rye grass pollen extract (WRGPE--Lolium perene) and house-dust mite extract (HDM--Dermatophagoides pteronyssinus) was examined in asthmatic children. Discriminant analysis of the data showed that, for the concentration of extracts used and the conditions of bronchial challenge for both allergens, the level of skin sensitivity to undiluted extract and the percentage fall in peak flow-rate on exercise best-predicted the outcome of bronchial challenge for WRGPE (100% of cases) and for HDM (89% of cases). The results suggest that it may be possible to predict allergenic bronchial-reactivity to different allergens in children by simple clinical methods, if conditions of provocation and potency of allergen extracts can be standardized.