By means of psychometric testing, we have determined the frequency of latent hepatic encephalopathy in a group of 19 cirrhotics with no clinical evidence of encephalopathy. Magnetic resonance imaging (MRI) of the brain was performed in order to determine whether morphological cerebral abnormalities were associated with latent encephalopathy. Nineteen age and educationally matched patients with normal liver function acted as controls. Significant differences (P less than 0.05) between cirrhotics and controls were found in tests of short-term visual memory and speed of reaction to light (cirrhotics 316 +/- 132 ms vs. controls 225 +/- 36 ms), sound (cirrhotics 361 +/- 152 ms vs. controls 236 +/- 52 ms) and choice (cirrhotics 651 +/- 190 ms vs. controls 406 +/- 101 ms) stimuli (all values mean +/- S.D.). Reitan trail test performance, however, was similar in both groups. (Trail A: cirrhotics 43 +/- 19 s vs. controls 35 +/- 13 s; Trail B: cirrhotics 105 +/- 66 s vs. controls 93 +/- 36 s.) In patients with cirrhosis, MRI revealed statistically significant increases in the maximum fissure width of right frontal sulci, right and left parietal sulci, inter-hemispheric fissure width and in bicaudate index. These changes, indicating cerebral atrophy, were largely confined to alcoholics. There was poor correlation between measurements of cerebral morphology and neuropsychological performance, only 10% of associations achieving statistical significance.