We found little evidence of important effects on pain outcomes associated with different characteristics of acupuncture or acupuncturists, including style of acupuncture, the frequency or duration of sessions, patient-practitioner interactions or the years of experience of the acupuncturists. Increased number of needles and more sessions appear to be associated with better outcomes when comparing acupuncture to non-acupuncture controls. This suggests that the dose of acupuncture is important. Trials designed to evaluate the potentially small differences in outcome associated with different acupuncture or acupuncturist characteristics are likely to require large sample sizes. There is room for a diversity of practice in acupuncture, and no strong evidence that such diversity leads to some patients receiving sub-optimal outcomes.