Multiple physiologic and psychologic factors contribute to the sensation of acute as well as chronic dyspnea. The causes of acute dyspnea frequently can be established by a brief history, physical examination, and chest radiograph. Appropriate therapy should be directed to reversing the specific etiology leading to the acute onset of breathlessness. Chronic dyspnea is probably the most common respiratory complaint of patients seeking medical care. Both aging and deconditioning may influence the development and severity of breathlessness in healthy and disease states. Pulmonary function testing, measurement of respiratory muscle strength, and cardiopulmonary exercise testing may be required to investigate the problem of chronic dyspnea. Once the diagnosis has been made, it is useful to measure or quantify breathlessness using clinical rating methods. This baseline assessment provides objective information for evaluating response to treatment. Initial therapy for improving chronic breathlessness should be directed at the specific cause of the problem. Additional strategies for reducing dyspnea include breathing techniques, exercise training, nutritional manipulations, psychologic interventions, respiratory muscle training, respiratory muscle rest, and sedative/hypnotic medications.