A portable system for measurement of stride time rhythmicity was developed using the technique of Hausdorff et al (2001a Arch. Phys. Med. Rehabil. 82 1050-6). Measurement was performed for an extended period of walking of 256 steps for each foot outside of the laboratory on 18 normal individuals and 20 patients referred with symptomatic vestibular impairment. Ten of the patients were reassessed following vestibular therapy. Gait rhythmicity measured by standard deviation (SD) stride time was found to be significantly higher in patients with vestibular impairment than in normal volunteers (mean +/- SD 60.3 +/- 39.8 ms versus 21.9 +/- 4.9 ms respectively, P < 0.001, t-test). The ten patients who returned following a course of vestibular rehabilitation displayed significant improvement in SD stride time following therapy (mean +/- SD 57.3 +/- 44.6 ms prior to and 40.9 +/- 23 ms following therapy, P = 0.01, Wilcoxon signed rank test). Gait rhythmicity measurement, specifically measurement of stride time variability, appears to be a powerful assessment tool for objective measurement of extent of impairment and response to therapy in patients with vestibular hypofunction.