One hundred and two stroke patients were studied. Thirty-three (32 per cent) were hypertensive by the WHO criteria. Eighty-three (83 per cent) had cerebral infarction and three patients suffered from spontaneous intracerebral haemorrhage. The mean left ventricular mass was calculated from echocardiographic measurements and compared with that of controls. Neither cases nor controls had valvular or congenital heart disease, or disease processes that may be associated with myocardial infiltration. Mean left ventricular mass of all cases was significantly greater than that of controls (p less than 0.025) and that of the cases over the age of 50 years was also significantly greater than that of controls of the same age (p less than 0.02). The clinically normotensive cases had greater left ventricular mass than the normotensive controls (p less than 0.02). Meanwhile left ventricular mass in patients aged 50 and under was not significantly different from the appropriate control group (p greater than 0.2). These data indicate that the frequency of arterial hypertension among victims of cerebral infarction is greater than may be ascertained clinically particularly in those over 50.