Most trials of non-ulcer dyspepsia (NUD) and Helicobacter pylori associated gastritis (HPAG) have not used validated methods of measuring symptoms. Three attributes are necessary for use of symptom severity scoring systems as outcome measures in clinical trials: reproducibility, responsiveness to change and validity compared to corroborating measures. The objective of this study was to establish that selected gastrointestinal symptoms recorded as a series of 5-point Likert Scales meet the 3 criteria for use as outcome measures in clinical trials. Patients with NUD (Helicobacter pylori-negative) and HPAG were studied. A preliminary assessment of 24 patients was used to select the 8 most frequently occurring and most severe symptoms. These symptoms were then scored in a further 55 patients to assess their utility as outcome measures. Observations were made at 3 time points, enrollment (T1), after 1 week with no intervention (T2) and after 4 weeks of therapy for either disease (T3). The study took place in a university hospital outpatient gastroenterology service. Symptom scores were reproducible before treatment (symptom scores at T1 and T2 were correlated), responsive (symptom scores changed after treatment between T2 and T3) and valid (symptom score changes corresponded to changes in general health status). Scoring of gastrointestinal symptom severity using 5-point Likert Scales satisfies the 3 criteria for use as outcome measures in clinical trials of NUD and HPAG.