We examined risk factors for coronary heart disease (CHD) by ambulatory blood pressure (BP) monitoring in 72 diabetic hypertensives who were hospitalized for the educational program. The patients were divided into two groups (CHD group, 19 subjects; and non-CHD group, 53 subjects) along with or without co-existing CHD. On ambulatory BP monitoring, no significant differences were found between the groups regarding BP values through the day. However, the CHD group had a significantly greater BP variability than non-CHD group. The result of logistic regression analysis demonstrated that nighttime systolic BP variability was an independent risk factor for CHD.