Motor function is either voluntary or involuntary. Nervous impulses that excite voluntary movements pass from the cerebral cortex to the motor neurons in the brain stem and the spinal cord. In turn, the axons of the motor neurons pass in to peripheral nerves, which innervate skeletal muscle fibres. Research in our group focuses on diseases of the motor neurons, which are the cell bodies of the peripheral nerves and on disorders of the nerve itself. Amyotrophic lateral sclerosis is a degenerative disease of the motor neurons causing increasing weakness leading to untimely death. Research deals with the natural history and by means of therapeutic trials we attempt to find cure for this dramatic disease. Disorders of the peripheral nerves are manifold. We concentrate on hereditary forms and on the so-called immune-mediated neuropathies. In the former, which are genetically determined an ongoing search for the disease-causing genes in collaboration with the Neurozintuigen laboratory has proven to be successful. In addition, the evolution of symptoms and signs is subject to study. As regards the inflammatory nerve diseases in which the immune attack is aimed at the myelin sheath around the nerve research centres on therapeutic interventions. Involuntary movements are generated by impulses from the corpus striatum, which is situated deep in the brain. Disorders of the corpus striatum are called extrapyramidal disorders. There can be a loss of involuntary movements of which Parkinson' s disease is a well-known example. In this disease symptoms can be alleviated either by administering minute lesions to the brain (stereotactical surgery) or by stimulation of parts of the brain. Conversely, there may be exaggerated movements, which is termed dystonia. Writer's cramp and blepharospasmus (inappropriate squeezing of the eyelids) are examples of dystonia. These disorders appear to respond very well to botulinum toxin. The mechanisms by which these diseases are caused and fine tuning of the therapeutical regimes are the key research objectives of the group who deals with extrapyramidal diseases.