BACKGROUND: The safety of fiberoptic bronchoscopy (FOB) in nonintubated critically ill patients with acute respiratory failure has not been extensively evaluated. We aimed to measure the incidence of intubation and the need to increase ventilatory support following FOB and to identify predictive factors for this event. METHODS: A prospective multicenter observational study was carried out in eight French adult intensive care units. The study included 169 FOB performed in patients with a PaO(2)/FiO(2) ratio ≤ 300. The main end-point was intubation rate. The secondary end-point was rate of increased ventilatory support defined as an increase in oxygen requirement >50 %, the need to start noninvasive positive pressure ventilation (NI-PPV) or increase NI-PPV support. RESULTS: Within 24 h, an increase in ventilatory support was required following 59 bronchoscopies (35 %), of which 25 (15 %) led to endotracheal intubation. The existence of chronic obstructive pulmonary disease (COPD; OR 5.2, 95 % CI 1.6-17.8; p = 0.007) or immunosuppression (OR 5.4, 95 % CI 1.7-17.2; p = 0.004] were significantly associated with the need for intubation in the multivariable analysis. None of the baseline physiological parameters including the PaO(2)/FiO(2) ratio was associated with intubation. CONCLUSIONS: Bronchoscopy is often followed by an increase in ventilatory support in hypoxemic critically ill patients, but less frequently by the need for intubation. COPD and immunosuppression are associated with the need for invasive ventilation in the 24 h following bronchoscopy.