Accuracy of echo-encephalography (EVG) was assessed by comparison with computer-tomography (CT) in a material of 49 children aged 2 weeks to 15.5 years and 158 adults aged 17 to 83 years. Third ventricle width could be measured on EVG in all the patients, and the correlations with CT values were excellent both in children and adults (r = 0.89 and r = 0.94, respectively). Lateral ventricle echoes could be recorded in 43 children (87.7%) and in 95 adults (60.1%). There were very good correlations between lateral ventricle size estimated as LVI (lateral ventricle index on EVG) and BI (body index on CT) both in children and adults (r = 0.84 and r = 0.86, respectively). In adults, a fairly large proportion (46.3%) of the patients where lateral ventricle echoes could be recorded, apparently had essentially normal ventricle systems, although there was evidence that these echoes could be recorded more easily from widened ventricles.