Early somatosensory evoked potentials were recorded in 33 patients with supratentorial brain tumors (9 benign tumors, 17 glioblastomas and 7 metastases). All the cases were studied with CT scan and all but 2 were surgically explored and histologically classified. Evoked potentials were statistically analyzed regarding the nature and site of the tumors. The temporal malignant tumors showed the most significant alterations in latencies, particularly for waves P25, N34 and P44.