Nonulcer (functional) dyspepsia is a common heterogenous disease resulting in upper gastrointestinal tract symptoms. Evidence would support that a subset of this disease is caused by H. pylori-induced gastritis. Despite the conflicting evidence, most studies evaluating H. pylori clearance and eradication, particularly the long-term studies, have observed clinical improvement in most subjects. Hill's concepts to distinguish causal from noncausal associations of an agent to a specific disease include the strength of association, consistency, specificity, temporality, biologic gradient, plausibility, coherence, experimental evidence, and analogy. There is considerable criticism of these nine aspects of epidemiologic evidence to judge whether an association is causal. These epidemiologic criteria to support that an association is causal are inappropriate when applied to H. pylori and NUD. First, the disease definition, based on clinical criteria, is imprecise, with poorly defined end points and considerable individual variability in interpretation. Second, it would appear that the cause is multifactorial, and thus, evaluation of one etiologic agent is inappropriate. In view of the potential factors to cause NUD, a scheme of treatment with a subset of eradication of H. pylori if present is advocated (Fig. 1). It is suggested that, because of the conflicting data in this area, subjects be entered into clinical trials, with eradication of H. pylori evaluated and long-term follow-up of symptoms accurately monitored.