In a double-blind cross-over trial of two 2-week periods, the clinical effect of progabide was compared to placebo. 16 patients with spasticity in a stationary phase completed the trial. 14 had multiple sclerosis, 2 hereditary spastic paraplegia. 5 were female and 11 male. The median age was 45.5 years (range 30-62 years). The median daily dosage of progabide was 24.3 mg/kg (range 14.3-32.7 mg/kg). During progabide treatment, there was a reduction in spastic hypertonia (P less than 0.01), a suppression of tendon reflexes (patellar) (P less than 0.01), and a reduction in the frequency of flexor spasms (P less than 0.05). No significant changes in voluntary power were registered. The global clinical impression revealed a therapeutic effect in 87% of the patients (95% confidence limits 61-98%). The improvement was judged as medium or important in 50% of the patients (95% confidence limits 23-77%). No side-effects or laboratory abnormalities were seen.