The authors report three microcystic meningiomas with its characteristic immunohistochemical findings and chromosomal pattern. Three patients with surgically treated microcystic meningioma were studied for its radiological, histopathological findings, and chromosomal analysis was done in the one patient. Tumors were convexity meningioma in the frontal area. The tumors were enhanced homogenously in the two, and enhanced in homogenously with multiple small cysts in the other one on preoperative magenetic resonance image. Pathological examination showed marked nuclear pleomorphism, many small cysts, hyaline thickening in blood vessel wall, and mucinous background, compatable to microcystic type. EMA and vimentin were positive on the immunohistochemical stain. Chromosomal analysis showed tetrasomies of chromosome 5, 13, 17, and 20, and trisomies of chromosome 6, 7, 9, 11, 12, 16, 19, and 21, which are quite different from those of benign meningioma.