The frequency and the correlation to leukoariosis were evaluated in the l00 cases of hypertension, in the 46 cases of diabetes mellitus and in 50 controls. The results were as follows: 1. The frequencies of leukoaraiosis were 35% in hypertension, 15% in diabetes mellitus and 4% in control. And there is significant difference in the frequency of leukoaraiosis between hypertension and control 2. The severity of leukoaraiosis significantly correlated with the level of diastolic blood poressure( p<0.05).