Acute respiratory failure (ARF) in oncology is relatively frequent. Nevertheless the information in the literature concerning solid tumours is sparse and not well documented. A large range of possible causes is at the origin of ARF. However, bacterial infection remains the principal cause of ARF. Opportunistic infections are more rare. Other causes are essentially linked to the tumour itself and the toxicity of the treatments (medication and radiation induced pneumonitis). Good management of the ARF necessitates the methodological gathering of clinical information and a chest X-ray. This permits the distinction of 3 broad situations: ARF with a normal chest X-ray, with focalised opacities and with diffuse opacities. Investigations to perform (angiography, bronchial fibroscopy, ECG, blood cultures...) and the treatment to undertake are specific to each of these situations.