Deep vein thrombosis is a potential complication in patients admitted to cardiac rehabilitation programs after acute coronary syndromes, episodes of acute congestive heart failure, and cardiac revascularization. A common clinical problem in these patients is to decide whether to start or continue physical training or not, given the risk of pulmonary embolism. Until definite evidence becomes available, careful patient selection and inpatient supervision may avoid the a priori withdrawal of such an important core component of cardiac rehabilitation programs.