Two-dimensional echocardiography is the method of choice for imaging and diagnosis in patients with hypertrophic cardiomyopathy. However, ultrasound examination of the left ventricular apex by transthoracic echocardiography is often inadequate so that hypertrophy localised to this region may be missed. The purpose of this study was to evaluate the use of multiplane transoesophageal echocardiography in the diagnosis and assessment of apical hypertrophic cardiomyopathy. Six patients with apical hypertrophic cardiomyopathy underwent transthoracic and multiple transoesophageal echocardiography. Assessment of the proximal left ventricle was possible in all patients by both techniques and normal wall thickness measurements were obtained. Assessment of the distal left ventricle by multiple transesophageal echococardiography revealed hypertrophy of the apex (range 1.7-2.9 cm) and less marked hypertrophy of the distal segments of the left ventricle in all 6 patients (1.4-2.2 cm). Examination of the papillary muscles was also possible and hypertrophy was detected in 2 patients. By transthoracic echocardiography, hypertrophy was detected in the distal left ventricle of 5 patients and values were less than those obtained by multiplane transoesophageal echocardiography. No papillary muscle hypertrophy was seen. The apical segment was imaged in only 4 patients and maximum thicknesses of the apical segment were greater by multiple transoesophageal echocardiographic examination than by transthoracic echocardiography (mean 2.25 ± 0.4 and 1.97 ± 0.3 cm, respectively). We conclude that apical hypertrophic cardiomyopathy may be difficult to diagnose using transthoracic echocardiography because of inconsistent imaging of the apical segment. The distribution of hypertrophy may be inappropriately assigned and the severity of wall thickening underestimated. Multiplane transoesophageal echocardiography allows high resolution imaging of all segments of the left ventricle, particularly the apex.