We evaluated etoricoxib, a novel COX-2–specific inhibitor, in 319 patients with chronic low back pain (LBP) in this double-blind, placebo-controlled trial. Patients were randomized to a 60 mg dose (n = 103) or 90 mg dose (n = 107) of etoricoxib, or placebo (n = 109), daily for 12 weeks. The primary endpoint was low back pain intensity scale (Visual Analog Scale of 0- to 100-mm) time-weighted average change from baseline over 4 weeks. Other endpoints included evaluation over 3 months of low back pain intensity scale, Roland-Morris Disability Questionnaire (RMDQ), low back pain bothersomeness scale, patient- and investigator-global assessments, Patient Health Survey (MOS SF-12), rescue acetaminophen use, and discontinuation due to lack of efficacy. Etoricoxib provided significant improvement from baseline versus placebo in pain intensity (4 weeks: 12.9 mm and 10.3 mm for 60-mg and 90-mg doses, P < .001 for each; 12 weeks: 10.5 mm and 7.5 mm for 60-mg and 90-mg doses, P = .001 and .018, respectively). Etoricoxib at either dose led to significant improvement in other endpoints, including RMDQ scores, bothersomeness scores and global assessments. Etoricoxib given once daily provided significant relief of symptoms, and disability associated with chronic LBP that was observed 1 week after initiating therapy, was maximal at 4 weeks, and was maintained over 3 months.