It has been exciting to witness the discovery that most peptic ulcers are caused by a bacterium that is relatively easy to eradicate. Most doctors now aim to give their patients the benefits of this unexpected breakthrough, but the new knowledge raises many questions. One is precisely which groups of patients to treat. We should restrict ourselves to the infected, but which of the many tests should we use to identify them? Having decided to treat, which of the plethora of regimens should we use? These questions have been particularly difficult to address at a time when knowledge and c1inical...