Understanding the pathophysiology of non-union is a prerequisite for successful treatment of this disorder. Fracture healing may be impeded by mechanical or biological factors as well as a combination of these. A thorough evaluation of each individual case before surgery is necessary to prevent either undertreatment or overtreatment. The whole spectrum of methods of internal fixation may be utilized for stabilization. To optimize the biological component, classic methods such as decortication and cancellous autograft may be employed. It is too early yet to determine if alternative techniques (e.g. ultrasound) will successfully replace these long-standing options. In any case, these newer modalities cannot supplant the need for skeletal stabilization. For infected pseudarthroses the first step is eradication of infection, after which measures can be taken to unite the fracture. Callus distraction has opened new and safe ways to treat large bone defects.