Mechanical ventilation is often life-saving but at the same time it is also hazardous. Definitive liberation from the ventilator should be realized at the earliest possible moment in a patient's clinical course, as both premature and delayed extubation may negatively affect morbidity and mortality. There is now substantial proof, that a two-step diagnostic approach is the most performing way to achieve smooth and successful weaning for these patients. The first step consists in careful evaluation of the suspected ready-to-wean patient (assessment of weaning readiness). Ascertained readiness to wean is confirmed by the second step, a stress test. A patient's tolerance to this trial usually leads to definite removal of the endotracheal tube, whereas contrarily - weaning failure - a structured and thorough diagnostic work-up regarding potentially reversible pathologies has to be carried out.