Abstract.[Purpose] The purpose of this study was to investigate how older adults adjust gait patterns when stepping over a ground-based obstacle under two different lighting conditions. [Subjects] A total of 10 communitydwelling healthy older adults (mean age, 67.9 ± 2.12 years; age range, 65-72 years) were enrolled in this study.[Methods] All participants stood quietly in a self-selected foot position on the floor. Each participant was then instructed to step over a 10 cm high wooden obstacle under two illumination conditions (1 and 200 lx) at a selfselected pace with the right leg in response to the verbal cue "GO", and continued walking with the left leg on a 5 m pathway. Toe clearances and step parameters were measured using an eight-camera motion analysis system.[Results] Under the low lighting condition, toe clearance of the trailing leg was significantly lower than under the normal lighting condition. However, no significant differences were observed in toe clearance of the lead leg, step velocity, stride length, step length, cadence, or swing/stance duration between the normal and low lighting conditions.[Conclusion] Older adults reduce toe clearance of the trailing leg under low lighting conditions while stepping over an obstacle, which places them at greater risk of falling.