Background & Aims: Antibodies against tumor necrosis factor-α are widely used to treat patients with Crohn's disease (CD). This study compared the effectiveness of infliximab and adalimumab, the 2most commonly used anti-tumor necrosis factor agents, in patients with CD. Methods: We conducted a retrospective cohort study by using U.S. Medicare data from 2006 through 2010. Patients with CD who were new users of infliximab (n= 1459) or adalimumab (n=871) after January 31, 2007, were included. Patients older than age 85 and those with rheumatoid arthritis, psoriasis, psoriatic arthritis, or ankylosing spondylitis were excluded. The primary outcome measures were disease persistence on therapy at week 26, surgery (including bowel resection, creation of an ostomy, or surgical treatment of a perforation or abscess), and hospitalization for CD. Propensity score-adjusted logistic and Cox regression were used to compute adjusted odds ratios or hazard ratios and 95% confidence intervals (CIs). Results: After 26 weeks of treatment, 49% of patients receiving infliximab remained on drug, compared with 47% of those receiving adalimumab (odds ratio, 0.98; 95% CI, 0.81-1.19). Fewer patients treated with infliximab underwent surgery than those treated with adalimumab, but this difference was not statistically significant (5.5 vs 6.9 surgeries per 100 person-years; hazard ratio, 0.79; 95% CI, 0.60-1.05). Rates of hospitalization did not differ between groups (hazard ratio, 0.88; 95% CI, 0.72-1.07). Conclusions: We observed similar effectiveness of infliximab and adalimumab for CD on the basis of 3clinically important outcome measures. © 2014 AGA Institute.