Aims: The aim of this study was to evaluate the capability of intraoperative ultrasonography (IOUSG) in identifying malignant intraparenchymal tumors during surgical intervention. Settings and Design: Forty patients with intrinsic malignant tumors were evaluated by using IOUSG. Materials and Methods: A real-time ultrasound scanner with a 3- or 5-MHz transducer was used for this study in all cases. The tip of the ultrasound probe was placed on the intact cranial dura mater and then moved in the sagittal and coronal planes. Results: Nineteen of forty patients had lesions that were primary malignant glial tumors. Five of them had previous surgery and radiotherapy. The remaining twenty-one had metastatic tumors. All lesions were well localized and malignant characteristics were well defined by IOUSG. Radiation-induced changes in five lesions in the surrounding brain and tumor parenchyma were described. Conclusion: In conclusion, IOUSG is not only helpful in localizing lesions but it can also be used in determining the malignant characteristics of lesions.