METHODS From a prospective and consecutive study on degenerative lumbar spine disorders containing 416 patients, all patients with a severely reduced or absent strength of the extensor hallucis longus muscle (n = 35) before surgery were identified. OBJECTIVE The incidence, diagnosis, and recovery after surgery of patients with L5 root compression syndromes and a severely reduced or absent power before surgery of the big toe extensor was evaluated. BACKGROUND The L5 root is commonly involved in disc herniation and central and lateral spinal stenosis. Whether motor recovery occurs after root decompression is not fully known. METHODS All patients underwent a conventional radiologic evaluation before surgery including one or more myelography, computed tomography scan, and magnetic resonance imaging. At examination before surgery, extensor hallucis longus-power was graded as normal, reduced, or severely reduced/absent, and the latter group is presented here. Surgical findings were registered. Clinical investigation was performed after 4, 12-, and 24-month follow-up periods. RESULTS A pronounced extensor hallucis longus paresis was seen in disc herniation in 20 of 187 patients, in lateral spinal stenosis in 10 of 122 patients, and central spinal stenosis 5 of 107 patients. Improvement of the paresis after surgery was equally common in disc herniation (15 of 20 patients) and lateral spinal stenosis (7 of 10 patients). Complete restitution was more common in disc herniation. None of the five patients with central spinal stenosis improved concerning paresis at the follow-up period. Improvement was most common during the first 4 months after surgery. No correlation between age or preoperative symptom duration and recovery was noted in either group. CONCLUSIONS The incidence of pronounced extensor hallucis longus paresis in lumbar nerve root compression varied between 5-11%. Recovery after surgery was common in disc herniation and lateral spinal stenosis but did not occur in central stenosis. Complete recovery was most common in disc herniation, and recovery occurred mainly during the first 4 months after surgery.