SUMMARYAssessment of intragastric urease activity by the13C‐urea breath test was performed before and after one day of dosing with either De‐Noltabs (tripotassium dicitrato bismuthate, one tablet 1 q.d.s.), Pepto‐Bismol liquid (bismuth salicylate 30 ml q.d.s.), or Roter tablets (bismuth subnitrate, one tablet q.d.s.) in twelveHelicobacter pylori‐positive patient volunteers. There was a significant decrease in the excess of13CO2after one day of dosing with each of the three bismuth compounds, but analysis of variance could detect no difference between the effects of the three compounds.Systemic absorption of bismuth following oral dosing with either Pepto‐Bismol or Roter is minimal, yet both compounds have a suppressive effect onH. pylorisimilar to that of De‐Noltab. This study suggests that the action of all three bismuth compounds is within the gastric lumen, and that systemic absorption of bismuth is not necessary for activity again