A variety of dosing schedules have been reported for the hyperventilation method of bronchoprovocation testing. To evaluate the effect of challenge technique on the bronchoconstrictive response, we had 16 subjects perform eucapnic voluntary hyperventilation (EVH) with dry, room temperature gas using four different dosing schedules. The hyperventilation challenge dosages included the following: (1) a target minute ventilation (VE) of 20xFEV1 for 6 min; (2) a target VE of 15xFEV1for 12 min; (3) an interrupted challenge with a target VE of 30xFEV1 for 2 min repeated 3 times; and (4) a target VE of 30xFEV1 for 6 min. Challenges 2, 3, and 4 gave identical absolute ventilatory challenges (identical factor FEV1xminutes) but at different VE dosages or time. Challenges 1 and 4 were of identical length, but different target VE. The mean postchallenge fall in FEV1 was 16.6±10.9%, 11.0±8.1%, 19.6±9.9%, and 26.7±11.3% for challenges 1, 2, 3, and 4, respectively. The response to an identical EVH challenge (FEV1x30 for 6 min) was reproducible when performed on separate days. We conclude that the challenge technique used for hyperventilation testing will have a significant impact on the bronchoconstrictive response and must be taken into account when interpreting study results. Tests may be quantitatively comparable over a narrow range of challenge time and VE. We recommend that a 6-min uninterrupted EVH challenge using dry, room temperature gas at a target VE of 30xFEV1 be adopted as the "standard"challenge.