Worldwide, over 400,000 patients have been treated with tumour necrosis factor (TNF)-alpha antagonists for indications that include rheumatoid arthritis, juvenile rheumatoid arthritis, inflammatory bowel disease, psoriatic arthritis and ankylosing spondylitis. Since their approval, concerns regarding safety have been raised. There is a risk of re-activation of granulomatous diseases, especially tuberculosis, and measures should be taken for detection and treatment of latent tuberculosis infections. Preliminary data suggest that anti-TNF therapy may be safe in chronic hepatitis C. However, TNF-alpha antagonists have resulted in re-activation of chronic hepatitis B if not given concurrently with antiviral therapy. Solid tumours do not appear to be increased with anti-TNF therapy. Variable rates of increased lymphoma risk have been described with anti-TNF therapy compared with the general population, although no increased risk was found compared with a rheumatoid arthritis population. Large phase II and III trials with TNF-alpha antagonists in advanced heart failure have shown trends towards a worse prognosis, and should therefore be avoided in this population. Both etanercept and infliximab are associated with the formation of autoantibodies, and these autoantibodies are rarely associated with any specific clinical syndrome. Rare cases of aplastic anaemia, pancytopenia, vasculitis and demyelination have been described with anti-TNF therapy. This chapter will discuss the safety profile and adverse events of the three commercially available TNF-alpha antagonists: etanercept, infliximab and adalimumab. The data presented in this review have been collected from published data, individual case reports or series, package inserts, the Food and Drug Administration postmarketing adverse events surveillance system, and abstracts from the American College of Rheumatology and European Congress of Rheumatology meetings for 2005.