Sarcoidosis is an inflammatory systemic disease with a prevalence of 20 to 50 of 100,000 inhabitants in West-Germany. Caused by an abnormal immune response to a hypothetic inhalative antigen, a granulomatous inflammation in mediastinal lymph nodes occurs, which frequently extends to the lung and sometimes to other tissues. The nervous system is clinically involved in 5% of the cases. The most frequent neurologic symptom is solitary or combined cranial nerve involvement. Cerebral manifestations are nodular or diffuse granulomatous infiltration of the brain and lymphocytic inflammation of the basal meninges. The rarer myelopathies and peripheral neuropathies often cause major neurological deficits. Muscular involvement, which is present in about half of the cases of sarcoidosis, normally causes clinically silent lesions. Chronic sarcoid myopathy or acute polymyositis are rare. Elements of the diagnostic procedure are X-ray of the lung, measurement of serum Angiotensin-Converting Enzyme (ACE)- and serum Lysozyme (LZM)-levels, Bronchoalveolar lavage, Gallium-67-scanning and Kveim-test. The diagnostic value of these investigations and the typical findings in CSF examination, computed tomography, nuclear magnetic resonance, myelography and electrophysiological investigation are presented. Suspected diagnosis of sarcoidosis should be confirmed by biopsy of non-caseating granulomatous lesions in involved tissues. An initially high dosage corticosteroid therapy for many months to several years is often effective. If this is not helpful in cerebral sarcoidosis whole brain irradiation with 1500 to 3000 rd administered in 10 single doses is indicated. Peripheral neuropathy refractory to therapy with orally administered cortisone should be treated with parenteral ultrahigh steroid therapy.