Intraoperative spinal sonography was performed 23 times in 20 patients with intramedullary spinal cord tumours, and the sonographic features were examined. Eight cases of astrocytoma were classified into three types: type 1, seen in 3 children, had intramedullary, circular or oval, hyperechogenic multiple tumour shadows; type 2 presented inter-multimyelomere, relatively well-defined single tumour shadows corresponding to grade III and I for two juvenile and aged cases each, respectively; and type 3 appeared ill-defined and diffusely infiltrating. The relationships between these types, the ages of patients and histological grades were considered a potential clue to mechanisms of occurrence and infiltration of astrocytoma. All 7 ependymomas had syrinxes, of three types; central canal was very large, the tumour lying within it like an island; or the tumour was in contact with a cephalocaudal side part of the syrinx; or the tumour had a syrinx or cyst. Sonographic images thus differ according to the tumour, but differential diagnosis is currently limited. Development of sonographic equipment, with upgrading its resolving power are hoped for.