Electroencephalograms of 12 patients with a recent lacunar infarct, 12 patients with a recent cortical infarct and 12 control patients were studied without previous information about the clinical features and the corresponding CT scan findings. EEG assessment included both visual and computerised analysis, in both the eyes closed and the eyes open condition. The specificity and the sensitivity of the EEG in the diagnosis of lacunar infarction in this study were both 0.8 (95% confidence limits 0.5-1). The positive predictive value of diagnosing a lacunar infarct on the basis of the EEG was 0.7 (95% confidence limits 0.4-0.9). The chance-corrected coefficient of agreement (kappa) between CT scanning and EEG was 0.75. Thus, in contrast to the results of previous studies, most EEGs of patients with recent lacunar infarction show rather specific abnormalities.