The stiff man syndrome is a rare CNS disease of a probably autoimmunologic etiology. The paper presents a case of a 45-year-old man hospitalized in our department of neurology because of trunk muscles rigidity and painful, paroxysmal, immobilizing muscle spasms with excessive sweating. On the neurological examination he presented with a restricted range of active movements of the trunk, increased muscle tone in the shoulder girdle, abdominal and paraspinal muscles, as well as lumbar hyperlordosis. The electromyographic needle examination revealed in all his trunk muscles an excess, continuous motor unit activity at rest, diminishing after benzodiazepine administration. This confirmed our initial diagnosis based on clinical symptoms and signs. No abnormalities were found in other examinations, including the cerebrospinal fluid analysis, CT of the brain, and the spinal cord MRI. The patient was treated with glucocorticoids and GABA-ergic drugs (vigabatrin, diazepam and baclofen) with good results, i.e. a considerable amelioration of his complaints. His motor ability has increased so much that he was fully self-dependent. No deterioration in his clinical status has been noted over three years since his discharge.