Twenty patients with high-grade gliomas were prospectively studied by pre- and postoperative transcranial color-coded real-time sonography (TCCS) and CT, to determine the sensitivity of TCCS in the identification of residual tumor and tumor regrowth. Each patient was subjected to preoperative and early postoperative CT (postoperative day 1) and TCCS examinations (postoperative days 6 to 8) and subsequent CT and TCCS follow-up examinations within a time interval of 6 weeks to 3 months. In eight patients, a total of 15 biopsy specimens were intraoperatively obtained from the wall of the resection cavity. Histological findings of intraoperative biopsy specimens showed that hyperechogenic areas adjacent to the resection cavity always contained residual tumor tissue. Early postoperative TCCS identified these hyperechogenic areas in 19 of 20 patients. In 12 patients, postoperative CT revealed contrast enhancement at the resection margin, indicating residual tumor. In these patients the extension of these hyperechogenic areas on TCCS exceeded the contrast-enhancing areas on CT by a mean of 58%. In eight patients, postoperative CT displayed no contrast enhancement along the border of resection. TCCS and histological findings indicated residual tumor in seven of these eight patients. The size of the hyperechogenic lesions identified by postoperative TCCS increased in time and follow-up examinations revealed that tumor regrowth arose from these hyperechogenic areas in all patients. In four patients, tumor regrowth was identified, on average 0.7 months earlier by TCCS than by CT. From these data we conclude that the sensitivity of TCCS in detection of residual tumor and tumor regrowth seems to be superior to CT. The value of TCCS requires further clarification by comparative studies including histology and MRI.