TNF -inhibitors. Tumour necrosis factor (TNF-a) is a proinflammatory cytokine that is involved with normal inflammatory and immune responses and with the pathogenesis of chronic inflammatory medical conditions, such as rheumatoid arthritis and Crohn's disease. The newest therapies for these conditions include the TNF-a biologic response modifiers: etanercept, infliximab and adalimumab. Used alone or in combination with methotrexate or other traditional disease-modifying drugs, all TNF-a inhibitors can produce improvements in the signs and symptoms associated with rheumatoid arthritis and can slow down progression of the joint destruction. Infliximab and adalimumab also seem to be useful in the Crohn's disease treatment. Worldwide, over half a million patients have been treated with TNF-a inhibitors and concerns regarding their safety have been raised. There is a risk of infections, tuberculosis reactivation, lymphoma, demyelinating diseases, heart failure, pancytopenia and drug-induced lupus. Careful patient selection and close monitoring for safety and efficacy will ensure successful use of these drugs.