With the use of antibiotics and improved dental care, osteomyelitis of the jaw is less common these days, But sometimes the management of osteomyelitis is more difficult because of appearance of resistant organisms to antibiotics. Treatment of the steomyelitis are incision and drainage, closed catheter irrigations, sequestrectomy, saucerization, hyperbaric ocygen therapy, and resection with or without bone graft. We experienced advanced osteomyelitis due to delayed treatment of left mandibular angle fracture. He have medical history of pschysoprenia. We decided to treat the patient with open reduction and closed cather irrigation. We achived reconsolidation of mandibular fracture accompanied by osteomyelitis by complete removal of inflammatory tissues, rigid fixation with miniplate and closed catheter irrigation.