Aims: The purpose was to assess the effect of discec-tomy surgery on postural control, lumbar perception and reßex activation of paraspinal muscles during sudden upper limb loading. Methods: The study included 20 patients selected for an operation for chronic low back pain due to disc herniation and 15 controls without chronic back pain. The paraspinal muscle responses for upper limb loading during unexpected and expected conditions were measured by surface EMG. The ability to sense lumbar rotation was assessed in a previously validated motorized trunk rotation unit in the seated position. The postural control was measured with a vertical force platform. Pain, disability and depression scores were recorded. Results: Patients had poorer lumbar perception (P=0.012) and postural control (P< 0.05) than healthy control subjects. The postural control remained unchanged but lumbar perception (P=0.054) and the lumbar feed-forward control (P=0.043) improved after the surgery. Conclusions: This study demonstrated impaired lumbar proprioception and postural control in sciatica patients. During short-term follow-up after operative treatment, postural control does not seem to change, but impaired lumbar proprioception and feed-forward control of paraspinal muscles seem to recover.