Severe unstable slipped capital femoral epiphysis (SCFE) usually requires some form of reduction before stabilization to avoid loss of motion and to prevent the development of early degenerative arthritis. Gentle manipulation and traction is being used to achieve reduction. The force applied with these techniques is uncontrolled and unpredictable, and may add to the pre-existing risk of avascular necrosis of the femoral head in such cases. The authors report a case of acute on chronic, severe, unstable SCFE in which reduction was satisfactorily achieved by gradual distraction using an external fixator across the hip joint. The patient did not show signs of avascular necrosis or chondrolysis at a follow-up of 38 months. Hip function was excellent with Iowa hip score of 98 at the final follow-up.