Cold air challenge (CACh) has been shown to discriminate between asthmatic and healthy young children. Hyperventilation with dry, room temperature air is a simplified alternative. We compared responsiveness in young asthmatic children between two standardized, single step protocols: dry air challenge performed as 6-minutes eucapnic hyperventilation with dry room temperature air, and CACh as 4-minutes hyperventilation. Response was measured as specific airway resistance by whole-body plethysmography and expressed as change from baseline in numbers of within-subject standard deviations (SDw). Challenge sequence was randomly assigned. A comparator challenge was performed 1 hour later if the first challenge gave a change of 3 SDw. Forty 2- to 5-year-old asthmatics were included. Responsiveness to cold versus dry air showed significant, but weak correlation (r2=0.34, p<0.0001), but responsiveness to CACh exceeded dry air challenge (7.6 vs 5.4 SDw, p<0.02). CACh seemed to induce reduction in response to the following dry air challenge (p < 0.01), while no such reduction was seen after dry air challenge. Conclusion: Responsiveness to CACh exceeded responsiveness to dry air challenge and CACh seemed to induce refractoriness in contrast to dry air challenge, probably because of the additional stimulus from airway cooling. This suggests CACh as the preferred method.