The clinical diagnosis of pulmonary embolism (PE) is difficult in coronary care units (CCUs) because many findings of PE are similar to those of acute coronary syndromes and heart failure. Immobilization of only 1 or 2 days may predispose to PE. Heart failure and acute myocardial infarction add to the risk. Dyspnea may be absent or occur only with exertion. The onset of dyspnea may occur over seconds to days. Orthopnea occurs with PE as well as heart failure. When the clinical probability and results of objective testing are discordant, the posttest probability of PE may be neither sufficiently high nor sufficiently low to permit therapeutic decisions. Objective scoring systems for clinical assessment have not been developed for patients in a CCU. d-dimer is likely to be of little value for the exclusion of PE in CCUs, because elevations occur with heart failure, unstable angina, and myocardial infarction. Computed tomographic pulmonary angiography with venous phase imaging of the low pelvic and proximal leg veins (computed tomographic venography) is recommended for imaging. Scintigraphy in women aged <50 years with normal or nearly normal results on chest x-ray may be the preferred imaging test to reduce the risk for radiation. Echocardiography with leg ultrasonography is a rapidly obtainable combination of bedside tests that may be useful for young patients and patients in extremis. In conclusion, the choice of diagnostic test depends on the clinical probability of PE, the condition of the patient, the availability of diagnostic tests, the risks of iodinated contrast material, radiation exposure, and cost.