A paradoxic diastolic intraventricular flow (directed from apex to base), caused by a pressure gradient between a small apical aneurysm and the main left ventricular cavity, connected by a narrow muscular tunnel, was detected by Doppler echocardiography in a 69 year old male with apical hypertrophic cardiomyopathy and effort angina. Coronary arteriography was normal and the clinical, electrocardiographic, echocardiographic and angiocardiographic features of the patient were otherwise typical of apical hypertrophic cardiomyopathy. Paradoxic diastolic gradients have been occasionally described in patients with hypertrophic cardiomyopathy, and indicate the existence of a sequestered apical cavity, which is frequently not detected by echocardiography. Identification of these gradients may have important clinical implications, since they have been related with a higher incidence of embolic events, severe ventricular arrhythmias and myocardial ischaemia and necrosis.