Aims: To explore the clinical value of foot extensor digi-torum brevis (EDB) muscle in patients with unilateral lumbosacral radiculopathy. Methods: This is a prospective study of 153 patients with low back pain (LBP) and unilateral lumbosacral radiculopathy. The average duration of symptoms was 94 (1–279) days and the average age of patients was 62 (18–75) years. Twenty þve patients had disc herniation with the involvement of L4 nerve root; 32 patients with the L5, and 36 with the S1. There were 31 patients with LBP only. Patients with a history of trauma of the lower legs, repetitive mechanical irritation, or systemic diseases were excluded. In all patients full clinical and neurological examination of the spine was performed. Clinical evaluation of the EDB with resisted dorsal ßexion of the toes was also made. The size and consistency of the EDB muscle was documented and compared with that of the opposite foot. Results: Seventeen patients with L5 and S1 nerve root involvement had isolated atrophy of the EDB muscle as this was compared to the EDB of the opposite side. Conclusions: Clinical evaluation of EDB muscle in patients with unilateral lumbosacral radiculopathy may aid the examiner in understanding the nature and level of the spinal nerve root pathology.