Spinal manipulation and chiropractic have been controversial at least partially due to a paucity of clinical scientific evidence of benefit. For example, reviews of the literature on randomized clinical trials (RCT's) of manipulative treatment for back pain have variably found evidence of benefit or insufficient evidence of benefit. A review of the existing clinical trials of spinal manipulation for neck pain concluded that most of the five existing RCT's were of relatively poor quality and that, despite some evidence for very short-term benefit, studies of higher quality will be needed in order to determine whether there is clinical benefit for this condition. This issue is important since neck pain is the second most common reason for presentation to chiropractors.