Mechanical and biological factors are responsible for non-unions of the proximal femur. We analyse the causal treatment-possibilities of the different localisations. Fifty-five patients with non-unions of the femoral neck (average age 53 years) with or without preexistent femoral head necrosis (44%) were treated by abduction osteotomy and followed up at regular intervals. In 15% of cases a second operation was necessary after an average of 9.3 years, including the early complications. At the latest control 90% of the patients were satisfied, with an average Harris hip score (HHS) of 91. The survivorship analysis with end point total hip replacement is favourable. In the same period 22 patients were treated with a total hip replacement. The 11 survivors had a clearly worse HHS of 65. The low-risk, technically demanding valgization osteotomy should be the first step in the treatment of femoral neck non-unions, even in the presence of femoral head necrosis; secondary operations are not compromised. Pertrochanteric non-unions are rare. The pertrochanteric fragment very often heals, leaving a lateral femoral neck non-union which can be treated with valgization osteotomy. Depending on the type of non-union and the age of the patient, anatomical reduction, medial displacement and valgization osteotomy can be employed. With the angulated plates of the ASIF (95 degrees, 120 degrees, 130 degrees) 23 of the 24 non-unions could be healed in one operation. Fourteen patients underwent total hip replacement. In the subtrochanteric area mechanical and vascular instability leads to implant failure or fatigue fracture. Rigid compression-re-osteosynthesis is the therapy of choice, the 95 degrees condylar plate the implant. Twenty-three of our documented 24 subtrochanteric non-unions healed, 4 in the presence of an infection. Multiple operations have been necessary in 2 of the 4 non-unions following a pathological fracture.