Background: The potential for disease modification of tumour necrosis factor antagonists in ulcerative colitis remains debated. Methods: We searched MEDLINE, the Cochrane Library and EMBASE. Clinical response/remission, mucosal healing, colectomy, disease-related hospitalisations, and adverse events were analysed by the methods of Peto and Der Simonian and Laird. Results: Five trials enrolled 3654 patients (anti-tumour necrosis factor = 2338). Anti-tumour necrosis factor therapy was more effective than placebo to induce and maintain clinical remission, with a number needed to treat of 12 (95% confidence interval [CI], 7-35) and 6 (95% CI, 4-12) for adalimumab and infliximab, respectively. Anti-tumour necrosis factor therapy was more effective than placebo to induce and maintain mucosal healing, with number needed to treat of 9 (95% CI, 5-48), 7 (95% CI, 5-17), 4 (95% CI, 3-6) for adalimumab, golimumab and infliximab, respectively. Only infliximab was associated with a reduced need for colectomy. Both infliximab and adalimumab were associated with less hospitalisations. Anti-tumour necrosis factor therapy did not increase the risk of adverse events. Conclusions: Anti-tumour necrosis factor therapy is more effective than placebo to induce and maintain clinical remission and mucosal healing. Both infliximab and adalimumab are associated with less hospitalisations. Infliximab reduces the need for colectomy. Anti-tumour necrosis factor therapy does not increase the risk of adverse events.