Localized suppuration involving the spinal cord is uncommon. A case of spinal subdural empyema is reported. The patient is 54-year-old male who had been suffering a diabetes mellitus but did not receive any treatment. His initial symptom was lumbago. Then he noticed a palpitation and general malaise which made him visit a hospital. Because he did not show any improvement by a fluid therapy, he was transferred to our institute for the further evaluation. On admission, physical examination showed no abnormality. Blood pressure was 170/90 mmHg, heart rate 128/min. and body temperature 37.1 degrees C suggesting a septic shock state. Neurological examination revealed slight consciousness disturbance, mild tetraparesis and bilateral hypesthesia lower than the level of L3. Laboratory examination showed the elevated leukocyte count and fasting blood sugar and urine ketone body levels of 20,500/mm3, 257 mg/dl and 226 mg/dl respectively. Blood culture proved a septicemia of Streptococcus agalactiae afterwards. On the second day of admission, lumbar puncture revealed a purulent cerebrospinal fluid, though X-ray CT of lumbar spine did not confirm a diagnosis. Spinal magnetic resonance imaging (MRI) revealed a widespread abnormal intensity of the spinal canal from the level of Th11 to L4. On the T1-weighted image (TR 300 msec., TE 40 msec.), cerebrospinal fluid space was abnormally isointense. On the T2-weighted image (TR 2,000 msec., TE 80 msec.), subdural and cerebrospinal space was filled with an abnormal high-intense lesion especially on the ventral side. He developed semicoma due to hydrocephalus following a intraventricular empyema. He was also complicated disseminated intravascular coagulation.(ABSTRACT TRUNCATED AT 250 WORDS)