Therapy of patients with chronic respiratory failure is mainly directed at minimizing symptoms in order to improve, or at least to prevent a deterioration of, patients' well-being. Under such circumstances, the perceived effect of therapies on patients' well-being and daily life represents the most important subjective outcome of treatment. Therefore, there is a need to provide a global estimate of health in patients on long term oxygen therapy or overnight home mechanical ventilation. The Maugeri Foundation Respiratory Failure Questionnaire (MRF28) is the first health status ("quality of life") questionnaire specifically developed for use in CRF and its items were selected to be applicable to patients with both obstructive and restrictive diseases. The Quality of Life Evaluation and Survival Study (QuESS) is a multinational study with the aim of re-evaluating the natural history of chronic respiratory failure in about 300 patients. To the authors knowledge, the Quality of Life Evaluation and Survival Study is the first study to evaluate the natural history of chronic respiratory failure in such a large number of subjects and with a complete set of data. In fact, both pathophysiologic and health status assessments will be made. Moreover, by collecting data on mortality, disease exacerbations and hospitalization, it will also be possible to verify the predictive ability of health status versus pathophysiology in terms of mortality and healthcare utilization.