SUMMARY Twenty eight patients with severe, intractable spasticity have been treated by chronic intrathecal administration of baclofen. An implantable programmable drug-administration-device (DAD) was used with a permanent intrathecal catheter. Infusion of 50 to 800 ug//day of baclofen completely abolished spasticity. Follow-up was up to two years. Therapeutic effect was documented by clinical assessment of tone, spasms and reflexes and by electrophysiological recordings of monoand polysynaptic reflex activity. Complications and untoward side-effects of the procedure were few. This procedure is recommended for spasticity of spinal origin refractory to physiotherapy and oral medication. It is a preferable alternative to ablative surgical intervention.After an upper motoneuron lesion in man, a spastic syndrome often develops with a delay of weeks or months. This is characterised by hyperactive monoand polysynaptic reflexes and a velocity dependent increase in muscle tone. Depending on the site of the lesion, the features of the motor disorder can vary considerably. In spinal cord transection the powerful inhibitory action of the vestibulo-spinal pathway (projecting from the lateral vestibular nucleus) on the tonic innervation offlexors is eliminated, leading to an increase in flexor muscle tone of the legs. Lesions of the reticulo-spinal pathways cause loss of inhibition of the flexion reflex, resulting in spontaneous and sometimes painful flexor spasms. On the other hand, extensor spasms can also occur. All these patients suffer frequently from severe disability having their legs in a fixed, usually flexed, position causing nursing problems and severe handicap in daily life.Flexor spasticity is often resistant to drugs in tolerable doses. Microsurgical procedures like selective peripheral neurotomy, posterior rhizotomy' and longitudinal myelotomy have been used. These interventions are designed to interrupt the spinal reflex arc or to reduce the afferent input to the dorsal horn.