The aim of this study was to investigate obstacle clearance and its variability in individuals with Alzheimer dementia (AD) as well as healthy elderly individuals while they approached and crossed an obstacle in their path. Fifteen people with AD and 15 age-matched/sex-matched healthy individuals (control group) participated in this study. Clinical assessment of both groups was performed by a neuropsychiatrist. Spatial-temporal parameters of 5 trials of unobstructed walking and 5 trials of obstacle crossing during walking (approach and crossing phases) were measured using a 3-dimensional optoelectronic system. The results indicated that individuals with AD showed higher variability in the approach phase for stride length and the horizontal distance from their trailing limb foot to the obstacle. However, their gait variability in the crossing phase was similar to the control group. In addition, the individuals with AD were found to walk slowly and with a short stride length in both conditions. In conclusion, individuals with AD had increased gait variability while approaching an obstacle during walking, indicating a deficit in planning to avoid obstacles that could be related to cognitive disorders. However, gait variability during the crossing phase may not be indicative of cognitive disorders in AD.