Echocardiography has evolved to become one of the most versatile modalities for diagnosing and guiding treatment of critically ill patients. Both transthoracic (TTE) and transesophageal echocardiography (TEE) provide real-time bedside information about a variety of structural and functional abnormalities of the heart as well as contractility, filling status and cardiac output, rendering it the method of choice for the assessment of cardiac function in the intensive care unit (ICU). Both approaches have its benefits and limitations. Although TTE remains the approach of choice, TEE has been shown to be of additional value in many instances in critically ill patients due to its ability to provide excellent visualisation of cardiac structures, its impact on patient management, and its low complication rate (2.6%). The present status of TEE in adult critical care is reviewed with special emphasis on its role as a diagnostic tool in several clinical scenarios, underlining its effects on clinical decision making but also as a monitoring adjunct. Conditions and settings in which TEE provides the most definitive diagnosis in the critically ill and injured are hemodynamically unstable patients with suboptimal TTE images or if mechanically ventilated, patients with suspected aortic dissection or aortic injury and other conditions in which TEE is superior to TTE (such as suspected endocarditis, cardiac or aortic source of emboli. The diagnostic, therapeutic and surgical impact on patient management in critically ill patients ranged from 44% to 99% (weighted mean 67.2%), 10% to 69% (weighted mean 36%), and 2% to 29% (weighted mean 14.1%), respectively, depending on patients and type of ICU. Since echocardiography provides different information than other devices for hemodynamic monitoring such as the pulmonary artery catheter the methods are therefore not competitive but rather complementary. The present body of evidence supporting the use of TEE in critically ill patients lacks prospective, randomized controlled studies focusing on end-points like cost-effectiveness, morbidity or mortality. However, present evidence as well as experience, points to the significant benefits which may be gained by the availability of echocardiography and especially TEE in ICUs, as well the necessity for a training of intensive care physicians.