Gait asymmetry during unobstructed walking in people with parkinson's disease (pD) has been well documented. However, under complex situations, such as environments with double obstacles, gait asymmetry remains poorly understood in PD. Therefore, the aim of this study was to analyze inter-limb asymmetry while crossing a single obstacle and double obstacles (with different distances between them) in people with PD and healthy older adults. Nineteen people with PD and 19 healthy older people performed three conditions: (i) walking with one obstacle (Single); (ii) walking with two obstacles with a 50 cm distance between them (Double-50); (iii) walking with two obstacles with a 108 cm distance between them (Double-108). The participants performed the obstacle crossing with both lower limbs. Asymmetry Index was calculated. We found that people with PD presented higher leading and trailing toe clearance asymmetry than healthy older people. In addition, participants increased asymmetry in the Double-50 compared to Single condition. It can be concluded that people with PD show higher asymmetry during obstacle crossing compared to healthy older people, independently of the number of obstacles. In addition, a challenging environment induces asymmetry during obstacle crossing in both people with pD and healthy older people. Tripping over obstacles has been identified as one of the prominent causes of falls in Parkinson's disease (PD) 1,2. There are several PD-related factors associated with trips and falls during walking, including unsymmetrical gait parameters 3. Gait asymmetry is characterized by a different pattern between the left and right limb extremities that reflects in unsymmetrical behavioral gait outcomes 4. Under healthy conditions, both limbs behave similarly, indicating a high level of symmetry during gait 3. However, pathologies such as PD result in marked spatial-temporal asymmetries during gait 3-6 , which is related to lesions in the basal ganglia region, the main area affected in PD 7,8. In PD, the depletion of dopamine in the basal ganglia is asymmetric between cerebral hemispheres, resulting in asymmetrical dysfunction of multiple basal ganglia circuitry 9. Because the basal ganglia provide phasic cues to several subcortical and cortical areas, e.g. the corpus callosum and supplementary motor area (SMA), uncoordinated bilateral control of gait can occur with PD 10-13. Substantial data have indicated that during level walking, people with PD present higher asymmetry in step length 13,14 swing phase 3-6 , and step duration 13,15 compared to healthy older people. Notwithstanding, behavioral outcomes underlying gait asymmetries under complex environments remain poorly understood in PD. To the best of our knowledge, to date, the effects on asymmetry of increasingly challenging models have been tested in postural control tasks 16 and during a single obstacle avoidance 17. Barbieri and colleagues 17 showed that people