Freezing of gait (FOG) is a specific gait disorder in Parkinson's Disease (PD). FOG occurs mainly in the medication-off state and usually improves with dopaminergic medication. FOG episodes can be clinically grouped into three patterns (small steps forward, trembling in place, complete akinesia) and five provoking subtypes (starting to walk hesitation, moving in tight quarters hesitation, reaching destination hesitation, turning hesitation, and walking in open space hesitation) [1]. FOG is a debilitating symptom, limiting activities of daily living, leading to falls or fall-related injuries, and diminishing quality of life [2]. The effect of deep brain stimulation of the subthalamic nucleus (STN-DBS) on freezing of gait (FOG) remains under debate since the prior results were conflicting. Whereas some studies [3,4] found an overall reduction of FOG under STN-DBS (although in most cases not to the same extent as non-axial symptoms), others reported no effect or even a deterioration of FOG [5e7]. The aim of this study was to evaluate the effect of STN-DBS on FOG with a special focus on the different FOG subtypes and patterns, as observed during a FOG provoking walking test performed before and at three follow ups after implantation. The VANTAGE study [8] e a multicenter, prospective, openlabel, non-randomized trial e assessed the effect of an implantable DBS system (Vercise™, Boston Scientific, Valencia, CA, USA) for bilateral stimulation of the STN in subjects with moderate to severe PD. In this preplanned sub-study, FOG was evaluated both subjectively (FOG questionnaire (FOGQ), the PDQ-39 mobility items, and FOG-specific items of the UPDRS II (items 13 [falls] and 14 [freezing])) and objectively with a standardized walking test provoking FOG (adapted from Ref. [1]). It was performed at baseline and at weeks 12, 26, and 52 postoperatively in the medication-on and-off state. STN-DBS was activated at all follow ups. The walking test was videotaped and made available for offline analysis by an independent and fully blinded rater (CB), who was unaware of the