Anaerobic soft tissue infections are still life threatening infections. Although their frequency is actually moderate; they remain severe because physicians are often insufficiently aware of them. Although the classification between myonecrosis and necrotizing fasciitis is still valid, these infections share so many points in common that they can be considered together. Their origin is often traumatic or surgical but may also be secondary to an ulcer or a small wound in a high-risk patient: arteriosclerotic, diabetic. Hypoxia, traumatic muscle crush, heavy bacterial contamination as well as incorrect antibiotic prophylaxis are the major reasons for their occurrence. Management consists of antibiotics adapted to both anaerobic and associated aerobic bacteria, large and early surgical debridement, but with conservative excision, and intensive hyperbaric oxygen therapy. Strict prevention measures must be applied to avoid their occurrence.