The previously described anti-spastic effect of oxcarbazepine and 10,11-dihydro-10-hydroxycarbamazepine was found accidentally in 2 patients undergoing a double-blind comparative study for evaluation of antiepileptic effect. In this study oxcarbazepine was given orally in doses of 300-2700 mg daily to one patient with transverse myelitis and to two patients with multiple sclerosis, all of whom had clinically disabling spasticity in the form of difficulty in walking, lower limb rigidity, spastic contractions of the lower limbs and ankle clonus. Anti-spastic effect was observed at doses between 600-1200 mg daily and consisted in a substantial decrease in the above symptoms of spasticity. The anti-spastic effect appears at a dose immediately below that which produces nausea, dizziness and somnolence.