Pulmonary embolism (PE) was believed to be a rare disease and often misdiagnosed in Thailand. Only a few cases of PE in Thai patients have been reported. The purpose of this study was to describe the characteristics of history, physical examination and laboratory investigations in Thai patients with PE. Forty-nine patients diagnosed as PE in Phramongkutklao Hospital between 1994 and 1998 were included in the study. All patients underwent complete history, physical examination and appropriate laboratory studies. The mean age of this patient group was 53 years. Thirty-four per cent of these patients were first suspected of lung embolism while the others were misdiagnosed as congestive heart failure, myocardial infarction, pneumonia or septic shock. The most common syndrome was isolated dyspnea. Interestingly, chronic thromboembolic pulmonary hypertension which is uncommonly found in western countries was diagnosed in 12 per cent of our patients. Dyspnea, pleuritic pain, leg swelling, cough, tachypnea, tachycardia and increased pulmonary component of second heart sound were common symptoms and signs. A high-probability ventilation/perfusion lung scan and deep vein thrombosis were demonstrated in 93 per cent and 55 per cent of our patients, respectively. The mortality rate was 10 per cent.