Research indicates that visual and verbal cues change gait spatiotemporal parameters in people with Parkinson's disease (PD) (Morris, Iansek, Matyas, & Summers, 1994a, 1994b). Previous studies show that utilizing harmonic analysis differentiates walking patterns between old and young adults (Menz, Lord, & Fitzpatrick, 2003). One purpose of this study is to examine differences in harmonic ratios between people with PD and healthy older adults and another is to determine the effect of visual and verbal cues on harmonic ratios of participants with PD when compared with their harmonic ratios during preferred walking. Eleven people with PD and 11 age- and gender-matched healthy older adults walkway under preferred walking conditions and visual and verbal conditions. The data showed significant group differences in preferred walking and across most experimental conditions. These data suggest that the external verbal cue given while walking was most effective for improving walking stability in people with PD.