Necrotizing fasciitis (NF) is a severe often life threatening bacterial infection. There are 2 main reasons to use hyperbaric oxygen (HBO2): the polymorphism of the bacterial flora with a predominance of anaerobes, either strict or aerotolerant; and the tissular necrosis due to an extensive disseminated microvascular obstruction within the infected area. Association of HBO2 to antibiotics and surgery is based on strong pathophysiological findings as well as on evidences from animal studies. Clinical evidence in human is still lacking even if published data supports its use in severe cases. Controversy on its use as a treatment for NF is caused more by the difficulty to dispose of a hyperbaric equipment allowing for the management of a patient in critical state, than by doubt on its real efficiency.