We present two cases of Werner's syndrome associated with intracranial meningioma. Characteristic clinical features of Werner's syndrome include short stature with slender extremities, premature senility, juvenile cataract, skin changes, a tendency to diabetes mellitus and familial occurrence. A 44-year-old female, who had been treated for diabetes mellitus, was diagnosed as having Werner's syndrome because of various characteristic features. A falx meningioma was incidentally found on CT scan, and was surgically removed. Her diabetes mellitus improved. The second case was a 28-year-old male was diagnosed as having Werner's syndrome, diabetes mellitus, juvenile cataract, together with diabetes insipidus, and liver dysfunction. He developed severe headache, gait disturbance and then became unconscious with right hemiparesis. He was found to have a parasagittal meningioma by CT scan and angiography. After removal of the tumor, diabetes mellitus, diabetes insipidus and liver dysfunction improved. The reported incidence of neoplasms associated with Werner's syndrome is about 10%. The majority of associated tumors were mesenchymal in origin. Ten meningiomas, 1 neurinoma and 2 gliomas are reported as associated tumors in the central nervous system. Most of the associated meningiomas were asymptomatic and found incidentally at autopsies or CT scans. Diabetes mellitus associated with Werner's syndrome is generally mild with high immunoreactive insulin value and is controllable by diet therapy and oral antidiabetic drugs. Daily profile of blood sugar improved after the removal of tumor in our cases. In 50 gm glucose tolerance test, tendency of delayed appearance of peak value, which is common in Werner's syndrome, was not altered in our cases. Discussion is made as to the association of Werner's syndrome with meningioma and diabetes mellitus.