604 patients with symptomatic knee osteoarthritis were randomized to treatment with either chondroitin sulfate, celecoxib, or placebo over a 6 month period. Patients were assessed for pain, function, perceived improvement and adverse events over the 6 months. The results from this study indicated that all three groups demonstrated a significant improvement from baseline over the 6 months. Both the chondroitin sulfate group and the celecoxib group demonstrated significantly greater improvement in pain and function compared to the placebo group after 6 months. There were no significant differences between the chondroitin sulfate group and the celecoxib group for pain or function. Incidence of adverse events was similar between the three groups.