Tumour necrosis factor alpha (TNF-alpha), a pro-inflammatory cytokine essential for the function of the immune system, has been implicated in the pathogenesis of idiopathic pulmonary fibrosis (IPF). Production of TNF-alpha is regulated at both the transcriptional and post-transcriptional levels by a number of factors including interleukin-10 (IL-10). We have shown that there is significant TNF-alpha activity in patients with IPF, despite the presence of significant amounts of IL-10 and Il-10R. IL-10 is thought to influence the tight translational repression of TNF-alpha mRNA in pulmonary macrophages. The essential element in this regulation is the AU-rich element (ARE) present in the 3' untranslated region of TNF-alpha. We hypothesised that polymorphism in the 3' UTR region of TNF-alpha explains the apparent failure of IL-10 to down regulate TNF-alpha in patients with IPF. Using single strand conformation polymorphism (SSCP) analysis, we have screened this region in 96 patients with IPF, using nine sets of overlapping PCR primers. All samples were successfully amplified for each primer set, but SSCP analysis was unable to detect point mutations or polymorphisms in the patients in any of the nine fragments. Results from this study suggest that the 3' UTR region of TNF-alpha is highly conserved in IPF and mutation of this region is unlikely to be involved in the pathogenesis of IPF.