The continuous separation capability of high-field asymmetric waveform ion mobility spectrometry (FAIMS) was used in combination with complementary techniques for probing biomolecular ions in the gas phase. Gas-phase conformers of the [M + 2H]2+ ion of bradykinin were examined using a combination of FAIMS, H/D exchange, and energy-loss measurements. When FAIMS data and H/D exchange data were analyzed separately, the presence of only two conformers of the [M + 2H]2+ ion of bradykinin could be detected. However, in an experiment in which FAIMS and H/D exchange were combined, at least four different conformers of the gas-phase [M + 2H]2+ ion of bradykinin were detected, including one of very low abundance. Cross sections calculated for the four conformers, based on energy-loss measurements, were 250, 240, 250, and 244 Å2, in order of decreasing abundance. Copyright © 2001 John Wiley & Sons, Ltd.