RESUMEN
<p><b>OBJECTIVE</b>To review the research progress on Type IV secretion system (T4SS) in Helicobacter pylori.</p><p><b>DATA SOURCES</b>The data used in this review were identified by searching of PUBMED (1995 - 2007) online resources using the key terms 'Type IV secretion system' and 'Helicobacter pylori'.</p><p><b>STUDY SELECTION</b>Mainly original articles and critical reviews written by major pioneer investigators of this field were selected.</p><p><b>RESULTS</b>The research progress on T4SS in Helicobacter pylori was summarized. The structure and function was discussed.</p><p><b>CONCLUSIONS</b>T4SS is not only involved in toxin secretion and injection of virulence factors into eukaryotic host target cells, but also involved in horizontal DNA transfer to other bacteria and eukaryotic cells, through DNA uptake from or release into the extracellular milieu. It provides a new insight into the pathogenicity of Helicobacter pylori and a novel target for antimicrobials development. However, many challenges remain for us in understanding the biological role of T4SS in Helicobacter pylori.</p>