Background: Osteoarthritis (OA) is a disorder involving deterioration of articular cartilage and underlying bone and is associated with symptoms of pain and disability. Glucosamine is a component of articular cartilage naturally synthesized in the body from glucose and incorporated into substances contained in the cartilage. It has been suggested that consumption of glucosamine may reduce the pain of OA and may have favorable effects on structural changes in the cartilage. This article presents a systematic review and meta-analysis of the effectiveness of orally consumed glucosamine sulfate (GS) on OA-related pain and joint structural changes. Methods: PubMed and Ovid Embase were searched using specific search terms to find randomized, double-blinded, placebo-controlled trials on the effects of GS on pain and/or joint-space narrowing. The outcome measure was the standardized mean difference (SMD), which was the improvement in the placebo groups minus the improvement in the GS groups divided by the pooled standard deviation. Results: There were 17 studies meeting the review criteria for pain, and the summary SMD was -0.35, with a 95% confidence interval (95% CI) = -0.54 to -0.16 (negative SMD is in favor of GS). Of the 17 studies, 7 showed a statistically significant reduction in pain from GS use. Four studies met the review criteria for joint space narrowing with a summary SMD = -0.10 (95% CI = -0.23 to +0.04). Studies without involvement of the commercial glucosamine industry had a lower (but still significant) pain reduction efficacy (summary SMD = -0.19, 95% CI = -0.39 to -0.02) than those with industry involvement. Several smaller dosages throughout the day had larger pain reduction effects than a single daily large dose (1500 mg). Conclusion: These data indicate that GS may have a small to moderate effect in reducing OA-related pain but little effect on joint-space narrowing. Until there is more definitive evidence, healthcare providers should be cautious in recommending use of GS to their patients. Because GS dosages used in studies to date resulted in mild and transient adverse effects, and these were similar to that experienced by patients receiving placebos, larger GS doses possibly could be investigated in future studies.