The objectives of the prospective randomized study are to investigate the clinically relevant change after anterior cervical decompression and fusion (ACDF) using measures of pain intensity (visual analog scale, VAS) and neck disability index (NDI). And to determine the number of subjects showing persistent pain and disability at 6-year follow-up. To investigate the possibility of differences in outcome between ACDF with the cervical intervertebral fusion cage (CIFC) and the Cloward procedure (CP). Clinically relevant change and residual, postoperative pain intensity and disability after ACDF have been investigated a little. Ninety-five patients with neck and radicular arm pain lasting for at least 6 months were randomly selected to receive ACDF with the CP or the CIFC. Questionnaires concerning pain and NDI were obtained from 83 patients (87%) at a mean follow-up time of 76 months (range 56-94 months). When evaluating clinical benefits regarding pain intensity 6 years after ACDF, according to different cut-off points and relative percentages, symptoms improved in 46-78% of patients. Improvement in NDI was seen in 18-20% of patients. Approximately 70% of the patients had persistent pain and disability at 6-year follow-up. There was no clinically important difference following CP versus CIFC. Thirty millimeter and 20% in pain intensity and NDI, respectively, are reasonable criteria to suggest a clinically relevant change after ACDF. Before patients undergo ACDF, they should be informed that they have an approximate 50% probability of achieving pain relief and little probability of functional improvement. The findings demonstrate that there is poor evidence for difference between CIFC and CP.