The growth rate of intracranial neoplasms has been studied extensively in three patients with the use of ultrasonic visualization methods. Normal and abnormal structural details in their brains have been compared to the brain structure of one patient without neoplastic disease. These patients' brains were scanned ultrasonically through the healed scalp, after a portion of the underlying calvaria had been removed during surgery for the neoplasm. Fissures, sulci, ventricles, cisterns, blood vessels, and some gray-white matter interfaces were visualized. Fine details of tumor proliferation and regression (glioblastoma multiforme and metastatic carcinoma) were accurately delineated. Ultrasound brain visualization has achieved sufficiently significant results to warrant its continued use through large skull defects to detect increase or decrease in the size of malignant neoplasia. The study also suggests that the substantial scientific effort required to provide comparable visualization through the intact skull be undertaken.