Objective: To determine whether trunk position sense is impaired in people with poststroke hemiparesis. Background: Good trunk stability is essential for balance and extremity use during daily functional activities and higher level tasks. Dynamic stability of the trunk requires adequate flexibility, muscle strength, neural control, and proprioception. While deficits of trunk muscle strength have been identified in people post-stroke, it is not clear whether they have adequate postural control and proprioception to ensure a stable foundation of balance to enable skilled extremity use. Trunk position sense is an essential element of trunk postural control. Even a small impairment in trunk position sense may contribute to trunk instability. However, a specific impairment of trunk position sense has not been reported in people post-stroke. Subjects: Twenty subjects with chronic stroke and 21 nonneurologically impaired subjects participated in the study. Main outcome measures: Trunk repositioning error during sitting forward flexion movements was assessed using an electromagnetic movement analysis system, Flock of Birds. Subjects post-stroke were also evaluated with clinical measures of balance (Berg Balance Scale), postural control (Postural Assessment Scale for Stroke), and extremity motor impairment severity (Fugl-Meyer Assessment-Motor Score). Results: There were significant differences in absolute trunk repositioning error between stroke and control groups in both the sagittal (P = 0.0001) and transverse (P = 0.0012) planes. Mean sagittal plane error: post-stroke: 6.9 ± 3.1 degrees, control: 3.2 ± 1.8 degrees; mean transverse plane error: post-stroke 2.1 ± 1.3 degrees, control: 1.0 ± 0.6 degrees. There was a significant negative correlation between sagittal plane absolute repositioning error and the Berg Balance Scale score (r = -0.49, P = 0.03), transverse plane absolute repositioning error and Berg Balance Scale score (r = 0.48, P = 0.03), and transverse plane repositioning error and the Postural Assessment Scale for Stroke score (r = -0.52, P = 0.02) Conclusions: Subjects with poststroke hemiparesis exhibit greater trunk repositioning error than age-matched controls. Trunk position sense retraining, emphasizing sagittal and transverse movements, should be further investigated as a potential poststroke intervention strategy to improve trunk balance and control. Copyright © 2008 Neurology Section, APTA.