Falls are common in patients with Huntington's disease, but the incidence, falling circumstances and contributing factors have never been examined. We recorded falls in 45 early to midstage Huntington's disease patients, both retrospectively (12 months) and prospectively (3 months). Fall rates were related to relevant baseline measures, including the Unified Huntington's Disease Rating Scale (UHDRS) and quantitative measures of balance (using angular velocity sensors) and gait (using a pressure-sensitive walkway). Balance and gait measures were compared between patients and 27 healthy age-matched controls. Twenty-seven patients (60%) reported two or more falls in the previous year and were classified as fallers. During prospective follow-up 40% reported at least one fall. A high proportion of falls (72.5%) caused minor injuries. Compared to nonfallers, fallers showed significantly higher scores for chorea, bradykinesia and aggression, as well as lower cognitive scores. Compared to controls, Huntington patients had a decreased gait velocity (1.15 m/s versus 1.45 m/s, P < 0.001) and a decreased stride length (1.29 m versus 1.52 m, P < 0.001). These abnormalities were all significantly greater in fallers compared to nonfallers. In addition, fallers had an increased stride length variability and a significantly greater trunk sway in medio-lateral direction compared to nonfallers. We conclude that falls are common in Huntington's disease. Contributing factors include a combination of "motor" deficits (mainly gait bradykinesia, stride variability and chorea, leading to excessive trunk sway), as well as cognitive decline and perhaps behavioral changes. These factors should be considered as future targets for therapies that aim to reduce falls in Huntington's disease.