Thirty-seven workers occupationally exposed to metallic mercury vapours were subjected to neurological examination and determination of visual (WPW) and somatosensory (SSPW) evoked potentials. In 6 cases slight sings of damage to the central nervous system was demonstrated. Prolonged WPW latency was noted in 15 cases. SSPW abnormalities were observed most frequently in the cortical components (13 cases), less frequently in the brainstem components (4 cases). Simultaneous WPW and SSPW changes were present in 10 cases. In the group of workers with changes of evoked potentials the mean urinary mercury levels were higher and the duration of exposure was longer than in the remaining workers. The use of multimodal electrophysiological methods increases the effectiveness of the diagnosis of subclinical damage to the nervous system in chronic mercury intoxication.