Persistent back pain in the presence of an intact posterior fusion is commonly seen and is often regarded as being psychogenic in origin. This paper discusses five patients, all of whom were chronically disabled by such pain; all five had a confirmed posterior and/or lateral fusion. In each case lateral discography identified the disc within the fused segment as the source of symptoms and pain relief was obtained with an anterior interbody fusion. This source of pain should be considered as a possibility in similar cases of failed back surgery.