Cardiac tamponade Is a medical emergency in which accurate recognition and prompt therapy are necessary for patient survival. We present the clinical and cytological findings of 5 patients who presented with cardiac tamponade as the initial manifestation of edracardiac malignancy. Pericardiocentesls not only afforded initial prompt relief of cardiac tamponade in all patients, but cytological examination of the pericardial fluid disclosed malignant cells In 4 patients, enabling us to make histological diagnosis of adenocarcinoma in 3 patients and suspected malignant cells in 1 patient. Thus in all 5 patients, the diagnosis of malignancy was initiaUy established by the cytological examination of the pericardial fluid. Tbe primary tumour was lung carcinoma in 3 patients, and unknown in 2, and tbe predominant histology was adenocarcinoma. All patients died within 10 weeks after admission.