To evaluate the behavior of cardiac arrhythmias (CA) and transient episodes of myocardial ischemia (TEMI), in relation to the circadian pattern of blood pressure in patients suffering from arterial hypertension, with or without echocardiographically ascertained left ventricular hypertrophy (LVH), we studied 128 patients, 87 men (M) and 41 women (F), aging from 21 to 76 years, subdivided into two groups: Group I, including 66 patients with LVH (45 M and 21 F; mean age of 53.7 +/- 9.1 years; Group II, including 62 patients without LVH (42 M and 20 F; mean age of 49.7 +/- 9.5 years). Office blood pressure (OBP) as well as nighttime ambulatory blood pressure (ABP) were higher in patients with LVH (P < .05 and P < .01). CA were present in a higher number of patients of Group I (P < .001): premature supraventricular beats (PSVB) 22.7 v 4.8%, supraventricular couplets (SVC) 36.4 v 16.1%, supraventricular tachycardia runs (SVT runs) 27.3 v 12.9%, ventricular ectopic beats (VEB) 25.6 v 8.0%, ventricular couplets (VC) 30.3 v 12.9%, ventricular tachycardia runs (VT runs) 12.1 v 3.2%. The absolute number of ectopic beats was also significantly higher in patients of Group I. Ventricular arrhythmias were significantly related to ASBP (r = 0.83, P < .01), to ADBP (r = 0.74, P < .01) and to heart rate (r = 0.87, P < .01) in patients of Group I. TEMI were more frequent in patients of Group I (73 v 41 episodes, 39.39% v 25.8% of patients, P < .01) and were related to ABP peaks. In fact, in both groups of patients all TEMI without heart rate increase and most TEMI with heart rate increase were registered between 6:00 and midnight, hours in which ABP values were higher. We conclude that hypertensives with LVH, but without clinical history of coronary heart disease, have a higher prevalence of ventricular arrhythmias and of transient episodes of myocardial ischemia in relation to the circadian pattern of ABP.