A multicentre study was undertaken to determine the diagnostic value of transoesophageal echocardiography (TOE) in tumours of the heart and pericardium. Forty-five cases were recensed: 24 myxomas, 1 fibroma, 1 hydatid cyst, 2 lymphomas, 3 sarcomas, 1 pleuropericardial cyst, 1 branchogenic cyst and 12 cardiac metastases. The diagnosis was made in all 45 cases by TOE but only in 35 cases by conventional transthoracic echocardiography which failed to recognise 2 myxomas, 1 hydatid cyst, 1 sarcoma, 2 paracardiac cysts and 4 cardiac metastases. The site of the tumour was identified 45 times by TOE compared with only 12 times by transthoracic echocardiography. However, the anatomical investigation of mediastinal tumours requires complementary computerised tomography. Moreover, TOE, like all other imaging techniques, is unable to predict the benign or malignant nature of the tumour, 1 leiomyosarcoma having been confused with a myxoma.