There is a lack of recognised markers for measuring gastrointestinal (GI) well-being and digestive symptoms in the general population. The aim of the present study was to demonstrate construct validity of a global assessment tool of GI well-being. In this randomised double-blind study, 197 adult women consumed either a probiotic fermented milk or a control dairy product daily during 4 weeks. GI well-being was assessed weekly using a single question and subjects indicated whether their GI well-being remained the same, improved or worsened compared with the baseline period. Responders for GI well-being were subjects reporting improvement for at least 2 weeks of the 4 weeks of intervention. Frequency of individual digestive symptoms was assessed weekly. Health-related quality of life (HRQoL) was measured at baseline and at the end of the study. Subjects reporting improvement of their GI well-being had a significantly (P< 0·05) lower frequency of combined digestive symptoms than individuals with no change, whereas subjects with worsened GI well-being had a significantly (P< 0·05) higher digestive symptom frequency. Number of weeks with reported GI well-being improvement was significantly (P< 0·05) correlated with the decrease in digestive symptoms (r 0·58) and the HRQoL digestive comfort dimension (r 0·47). When compared with non-responders, responders had significantly (P< 0·0001) fewer average digestive symptoms and higher scores on digestive comfort of the HRQoL questionnaire. The data provide construct validity for a single-item questionnaire as a measure of GI well-being improvement. These data support the use of this questionnaire as an end point for nutritional intervention in the general population.