To compare the efficacy of various psychometric and neurophysiological tests in the detection of latent hepatic encephalopathy (LHE) cerebral functions were studied in 146 patients with liver cirrhosis but without overt encephalopathy and in 146 matched controls. Patients with liver cirrhosis scored significantly worse than controls in 8 out of 11 tests. Best discrimination between patients with cirrhosis and controls was obtained by testing for reaction time to white and colored light with a reaction time apparatus (DTG), and with the digit symbol (UT1) and block design test (UT4), i.e. with two Wechsler adult intelligence scale performance tests. Thirtyseven out of 146 (25%) patients with cirrhosis reveiled an abnormal result with the DTG alone. A combination of the DTG, UT1 and UT4 yielded the diagnosis in 44 (30%) patients. LHE correlated with the severity of the disease (Child-Pugh classification) but not with its etiology or with portasystemic shunting. In the Federal Republic of Germany about 300,000 subjects suffer from liver cirrhosis. Based on our results 100,000 of them may have LHE.