A group of 42 adult patients with supratentorial brain tumors were studied with computed tomography (CT or/and NMR) and brain-stem evoked potentials (BAEPs). 12 patients had meningiomas and 30 had malignant tumors (gliomas and metastases). The latencies of wave V and of the interpeak latency I-III, III-V and I-V were evaluated both on the lesion side and the opposite side. In meningiomas mean latencies did not show significant differences from normal, while mean latencies in malignant tumors were significantly prolonged, except for the I-III interpeak latency. The results of this study demonstrate that BAEPs may be altered by supratentorial brain tumors. This examination appears to be useful in the monitoring of these lesions after treatment.