In this double-blind, placebo-controlled trial, we assessed the efficacy and safety of beef tallow extract (BTE) including Cis-9-cetylmyristoleate in patients with arthritis. Between May and December 2003, we selected 80 patients (n=80) who showed/manifested arthritic symptoms and whose radiological findings were suggestive of arthritis, and randomly assigned them to placebo-controlled (n=40) and treatment group (n=40). The placebo (corn starch 350 mg) and BTE (208 mg) were orally administered to placebo-controlled and treatment group three times a day, respectively. We assessed the efficacy and safety based on the visual analogue scale (V AS) and modified knee society knee scores (MKSKS) at baseline and endpoint, respectively. To assess the safety, we monitored the adverse effects noted in liver, kidney, cardiovascular and gastrointestinal system for 3 weeks. Then, we performed not only a questionnaire study but also laboratory tests (e.g., liver function test, kidney function test, urinalysis, electrocardiography [EKG], complete blood cell counts [CBC] and chest X-ray). For statistical analysis, Student (-test and paired (-test were done using SPSS■ Version 11.0. Statistical significance was set at p < 0.05. The scores between V AS and MKSKS showed statistical significance (p < 0.05) with an improvement of $69.2\%$ (27/39) and $3.8\%$ (21/39) of treatment-group patients, respectively. Abnormal laboratory findings were noted in neither placebo-controlled nor treatment group. In conclusion, our results indicate that the administration of BTE was a safe and effective treatment regimen for patients with arthritis. In addition, the efficacy of BTE was more remarkable in alleviating the symptoms rather than improving the function.