AbstractAt Royal Perth Hospital, Western Australia in April 1982, spiral bacteria were first cultured from a gastric biopsy specimen. Several important taxonomic features were identified which indicated that these bacteria represented a new genus. In October 1989 the new genus nameHelicobacterwas published.Helicobacter pyloriovercomes gastric defence mechanisms by means of its powerful urease enzyme, by its spiral shape allowing it to penetrate mucus, by adherence to the gastric mucosa and by various mechanisms which enable it to evade the immune response.