Lumbar and cervical fusion in the degenerative spine is frequently performed. Certain criteria have been established when a fusion should be considered. However, even these are not universally accepted. Strict prospective studies are needed to determine when a fusion of the degenerative, cervical, and lumbar spine is indicated. Patients with severe radicular pain may be considered for surgery after a comprehensive trial of conservative management. Fusion is usually necessary after a cervical discectomy, especially when spondylosis or osteophytic compression is present. Lumbar fusion is rarely indicated for routine discectomy. In patients with mechanical back or neck pain, surgery should only be considered after conservative measures have been exhausted and a radiographic abnormality is present at the symptomatic level, perhaps with pain concordant with discographic findings. Careful patient selection is the key to obtaining favorable surgical outcomes. In many cases, the goal may be a return to functionality rather than achieving a completely asymptomatic state.