We studied the role of brain electrical activity mapping (BEAM) in the assessment of neuropsychiatric disturbances in 48 cirrhotic patients without clinical evidence of hepatic encephalopathy (no HE, n = 19), with subclinical HE (grade 0, denoting pathological psychometric tests, n = 13) and mild-to-moderate HE (grade I, n = 6; grade II, n = 10). Results were compared with 23 healthy controls. BEAM variables quantified were: (i) the peak frequency (PF); (ii) the amplitude of PF; and (iii) the topographic localization of the maximum peak amplitude digitized for quantification by using a coordinate system. Mean amplitudes and their topographic localization in the following frequency-bands were analysed: delta (1.0-3.5 Hz), theta (4.0-7.5 Hz), alpha 1 (8.0-9.5 Hz), alpha 2 (10.0-11.5 Hz), beta 1 (12.0-15.5 Hz), beta 2 (16.0-19.5 Hz), and beta 3 (20.0-23.5 Hz). The PF was significantly slower in all HE patients than in healthy controls (8.5 +/- 2.0 Hz v. 10.1 +/- 1.0 Hz, P< 0.001). Even in no HE, the PF was significantly slower than in controls (8.6 +/- 1.5 Hz v. 10.1 +/- 1.0 Hz, P< 0.01). No relevant topographic differences of PF were observed. The mean amplitudes of the following bands differed significantly between controls and patients: theta (increased in HE, P< 0.05), alpha 2 (decreased in HE, P< 0.05), and beta 2 and beta 3 (increased in HE, (P < 0.05). In HE patients, the topographic localization of all beta bands showed a significant shift from parieto-occipital areas to central areas of the cortex. We conclude that BEAM is a sensitive tool for detecting neuropsychiatric disturbances in cirrhotics with no HE and with subclinical HE. The combination of PF in the theta band, increased mean amplitude in the beta 2 band, and the localization of the latter band in the frontocentral area of the cortex is an objective and sensitive tool for identifying neuropsychiatric disturbances in 85% of cirrhotic patients with no HE. Further studies are required to determine the clinical implications of these abnormal findings in the absence of overt clinical symptoms.